It sounds to me as if what you need to do is to have a frank conversation with your partner about things. Sexual attraction for a partner can ebb and flow, and one option might be that some good communication would improve things between the two of you on that front. Alternatively, you could stay together in an "open" relationship, where the value of your partnership can be preserved but not at the cost of your sexuality. The point is that between the two of you, communicating well about what you have and what you (now) lack, there might be some creative problem-solving that would give a more optimal result than the options you are currently considering.
I'd say most of what you're asking isn't something that philosophers have any special insight into—at least if "important" means "most likely to make for success." When it comes to questions about how daily life actually works, philosophers are in the same boat as everyone else.
I suppose someone might say that we can make a distinction between what's likely to work best and what's most important in some not-merely-practical sense. Philosophers might then have something to say, but I find it hard to image that there'd be a single compelling answer.
Your last question, however, did pique my curiosity: could there be a romantic relationship without sex or affection? That's a conceptual matter, and is therefore the sort of thing that spins philosophers' wheels. A romantic relationship without sex is clearly possible. Couples who are "saving themselves for marriage" provide lots of examples. And it might be that many people would call an ongoing sexual relationship a romantic relationship even if the people involved didn't really care like or care about one another. I'm guessing, however, that my hesitation here tells us something: to count as a romantic relationship, it may well be that feelings of affection and physical attraction have to be part of the package. However, if we take away sex and affection, it's not clear what reason we'd have to use the term "romantic."
That's where I'd take my stand if I had to, but I suspect it doesn't have much to do with what you were trying to figure out. I dare say that there's a good deal of empirical literature on the practical questions. Here's one sample from a quick bit of googling. And I even recall one persistent tidbit from other things I've read: apparently (sorry; can't recall the sources) how couple fight can be a good predictor of whether their relationship will last. In particular, if they treat each other with contempt, that's a bad sign. And so maybe that suggests a guess about what matters: treating each other with real respect.
Great question. Today, I think most people do think of a Platonic relationship as an intimate friendship without sex. The first time such a notion was explicitly identified was in the Renaissance when the philosopher / translator of Plato, Marsilio Ficino coined the term. Marsilio first called it "Socratic love," but then changed the term to "Platonic love" and he mostly applied it to male friendship. Marsilio's shared Platonic love with Giovanni Cavalcanti, a young man famous for his beauty. He maintained that you can be in awe with the beauty of your Platonic friend, but you must not touch or smell him. You refer to a Platonic friendship with an opposite gender; while Marsilio did not address this, Plato himself had female students and, given his high view of women in the Republic (women could be rulers), there is no reason why what we call Platonic love needs to be same-gender.
I would say one of the key elements in what is love in the Platonic tradition is that, whether or not sex is involved, when you love someone you must yearn for or desire their good. For more on such matters, you might check out the book *What Philosophy can tell you about your lover" edited by Sharon Kaye, chapter 8: "Platonic Lovers."
I am not aware of psychological studies on the nature of Platonic loves, but that chapter will help you get started in further philosophical reflection on love.
Great question! Consider, with apologies for the homeliness of this analogy: Does fastening your seat belt in a car or on an airplane indicate a lack of trust in the vehicle(s) or a lack of love for the pilot or driver or other pilots and drivers? I suspect one might have lots of trust and love and yet be realistic that sometimes the very unlikely and (almost) impossible does occur. In a prenuptial agreement, both parties may be passionately committed to each other and yet, out of a "realistic" understanding of the rate of divorce, they want assurance that there is a fair outcome if (heaven forbid) the life-long vow of commitment is not bourn out), it seems practically wise to have a safety net.
I'm wary of these sorts of comparatives: best, closest.
We all have many relationships that mean a great deal to us, and we do not need to make sure that one of them is "best", "closest". Indeed, if there is anything I've learned about relationships, it is how destructive those sorts of expectations can be. One certainly should not feel that if some interest one has isn't shared by one's partner, then it isn't worthwhile, or has to be sacrificed to the relationship, or what have you. That kind of thing starts to sound to me kind of clingy and possessive.
There may be some counterexamples, but in most healthy couples I know, both partners have interests that are not shared (or not really embraced) by the other partner, and their freedom to explore and nurture those interests with other friends or family is part of what keeps them growing, both individually and as a couple.
On the one hand, there are no doubt good reasons for incest taboos. For one thing, family life might become hopelessly complicated if sexual liaisons between first-degree relatives were common. To that we can add that when close relatives have children, the risk that their child will have birth defects goes up, and to that we can add further that if such situations became common, there might be unfortunate effects on the genetic variability of the larger population.
That said, your first cousin is not a first-degree relative. Furthermore, the fact that a practice would be problematic if everyone engaged in it doesn't mean that it's automatically wrong. After all, if everyone were to practice celibacy, the human race would die out. But even if you think that would be a bad thing, you presumably don't think it means that no one should decide to be celibate. More relevantly: while it's true that when first cousins have children the risks of birth defects increase somewhat, the increase is on a par with the risk of birth defects for children of mothers over 40. Here is a brief discussion. To this we could add that if that were the worry, then birth control would address it.
So it's hard to see that there's much in the way of serious objections to the case you describe. True, some people/cultures feel differently, but as you point out, others don't. There's no reason to think that groups who approve of first-cousin relationships are somehow morally confused.
Of course, some people will have a sort of surd "Ick" reaction. But that doesn't tell us much. After all, some people have that reaction to interracial marriage, or to homosexual relationships. The reaction doesn't stand up to scrutiny in those cases, and it's hard to see why it would fare any better here.
I cannot resist at least trying to respond to your question, but please know that this is a rather personal matter and many would think this is a matter for you to consider in light of respecting your partner and your own judgment about the consequences of making such a disclosure. Perhaps, though, I can be helpful in highlighting some factors to consider.
I suggest that promises to others can be (but are not always) binding even if the relationship ends. So, while obviously after a divorce or break-up one is not bound to (sexual) fidelity with one's x even if that had been promised with a vow, but there may be promises such as promising not to disclose information or secrets that were shared with the understanding that this was to be strictly confidential. I suggest that if the relationship you had (or you are about to break off) was built on the basis of trust and an explicit (or implicit) understanding that either of you would disclose any infidelity if it occurred, that would be a good reason to make the disclosure even as or after the relationship ends. This would be a natural conclusion based on the (at least ostensible) obligation to keep the promises we make (unless these "promises" were coerced, etc) and maintain one's integrity. On the other hand, one might also take into account the complex matters involved in "cheating." I have been assuming that the "cheating" you are referring to involves sexual infidelity, but there are all kinds of ways of (as it were) cheating in a committed relationship. If I am neglecting and completely ignoring my partner's needs or her central projects right now (as I have done, let us imagine, for years) and am focussing only on, say, writing a response to you on the "AskPhilosophers" site instead of being present and responsive to her, then I am (in a sense) right now cheating on my partner, the one with whom I have vowed to love, cherish, and to share our lives together. So, I suggest that sexual unfaithfulness is not the only kind of unfaithfulness (or acts done that are not disclosed). And thus....
I suggest that the key concerns lies in what the "cheating" involved means. Personally, I would regard sexual "cheating" as less grave and a reason for feeling hurt than the emotional withdrawal of love. If my partner "cheated" but claimed she still loves me and she "cheated" at a philosophy conference when she met a former partner and was intoxicated and she was angry about my neglecting her in order to work on "AskPhilosophers," this would or should be (for me) seem less grave and hurtful than if she "cheated" on the grounds that she no longer loves me. So, I suggest that in making your decision you might consider how much weight you think you ought to give to physical intimacy and the more general concern with your beloved's (or former beloved's) well being. If sharing that information is likely to lead to depression, self-hatred, and more by the X, that would count against disclosure. But if sharing might enable you both to change for the better, while you may no longer be lovers, this could be, in the words of the movie Casablanca, be the start of a beautiful friendship.
Sure, some people can only be in love with people who are entirely different from them. One of the nice things about romance is that it brings very different people together and we often wonder why they are together, what they see in each other, and whether it will last. Hollywood romances are based on such differences. It would be very boring if we always fell in love with people rather like us, although we often do, and surely there is no right or wrong in cases like this.
Did you make a mistake? Certainly not, you gave it a try, it did not work out and so on to the next relationship. It would not be surprising though if you fall in love again, perhaps for a long time, with someone who is again not your intellectual equal, since while you might enjoy the cut and thrust of discussion, it is sometimes pleasant to give the rational rapier a bit of a rest.
My Valentine's Day reflections on the topic.
There is an old saying (I'm told it originates with Kant, but I am not sure about that), which goes, "'ought' implies 'can.'" The idea is that you can only be held responsible or have an obligation to do something (you "ought" to do it) if it is something that is under your control. Do you suppose that emotions (such as love) are under one's voluntary control? I'm inclined to doubt that (with a few reservations, which I will get to momently). But if love is not something that you can voluntarily control, then it makes no sense to say that you have an obligation to love your mother (or anyone else, for that matter).
On the other hand, we do also evaluate people on the basis of how they feel about things, and on the basis of emotions they have and display. We same that some anger, for example, is inappropriate, and we regard most examples of hatred as at least unfortunate, if not contemptible. Does this make sense? I think it does make some sense, in that at least one of the things we value (positively or negatively) in people are their characters, and this includes emotions and such. So does this violate "ought" implies "can"? That seems to me to be more complicated, because while it does seem implausible to say that we can turn emotions on and off like faucets, it also seems plausible to say that the sorts of characteristics we have are at least to some extent the result of things we are able to do--for example, we can train ourselves to improve upon the way we might react to certain things (go to anger management therapy, for example, or biting our tongues when we feel impulses to say things that are cruel or hateful). people who have (or display) bad character may not be able to act any differently at the moment, but it still makes sense for us to hold them responsible for not having done the character-building that would have made them better people who would not have behaved so badly in that moment.
So back to loving your mother. On the one hand, if what you find unlovable about her are her values, it could well be that your reaction is simply the right one. There may be some respect(s) in which one need to respect and recognize the special relationship of parent and child, but I can't see why someone who is a bad person deserves to be loved by anyone, child or otherwise. On the other hand, before you take this as an excuse, you might do some serious double checking on your own values, which are leading you to reject hers. All I can know for sure, if yours and hers conflict, is that at least one of you is wrong. It might not be her, and it also might be both of you!
I suppose the ideal is that love between a parent and a child is sustained quite naturally, and is actually deserved in both cases. But maybe that is not going to be possible in this case. If so, then as I said, there are still some reasonable constraints about how you should respond to your mother (because she is your mother), having to do with civility and respect for her role in your life. There are certain duties and kinds of loyalties that we reasonably expect along these lines (though as I have already indicated, these are defeasible, if those to whom we normally would supply these have violated the ground for such things badly enough--an abusive parent, for example, may reasonably be thought to have lost any claim even on the most basic forms of loyalty from the child he or she has abused). At the very, very least, your mother deserves from you the kind of civil and polite responses you would provide as a matter of common decency.
But I can't help but wonder if perhaps you can do better than this. I don't know your mother or her values that you object to. But I suspect that civil discussion and allowing her to explain those values to you, and why they are important to her might at least allow you to achieve a level of understanding that would allow you to be more tolerant. Tolerance is not the same as love, I agree, but it's a start!
Let's start with a distinction between your feelings and your actions. I might be flattered that someone is in love with me; the feeling isn't wrong by itself. But if I lead the person on when I don't feel the same way about them, that's another matter.
So the question is: are you taking advantage of him? There are a couple of obvious things to ask. If the tables were turned, how would you feel about what was going on? And as things actually stand, how do you think he'd react if he found out how you really feel?
That second question is the really important one. If you suspect he'd be unhappy that you're accepting his gifts and attentions even though you don't love him and love someone else, then it's pretty obvious: you're using him as a means to your own ends. That's wrong.
Of course there's another possibility: the fact that you enjoy not just his gifts but also his attention and care could mean that there's a difference between the way you say you feel about him (even to yourself) and how you really feel. Since we're quite capable of fooling ourselves about this sort of thing, that's a possibility worth taking seriously.