This hypothesis does not explain why people tend to fall in love with opposite sex, while simulating brains more similar to your own should be easier.
That's a fine point! I think I understand pretty well why there's usually not sexual attraction between people of the same sex...If you take "love" and subtract the sex part out of it, is that what a close friendship looks like, or is there more to it than that?
The Fundamental Question of Rationality is "Why do you believe what you believe?". You don't seem to answer it in your post.
There's probably more to this. What I'm about to describe may be more about intimacy than about love, per se. It could just as easily be the intimate understanding between archfoes as star-crossed lovers.
It seems to me that a lot of behaviors and feelings around love can be explained just as people simulating other minds in high fidelity, and then experiencing a shadow of the simulation's feelings as their own via empathy or mirror neurons.
So, I simulate you experiencing something, and then I feel a diluted version of what you would actually feel if you experienced it in real life. I emphathize with my model of you kind of like how I'd empathize with the real you if I were observing you.
Love at first sight, then, would be me feeling intense feelings about my model of you, but it wouldn't be a correct model. I'd be projecting a stereotype onto you, using your appearance as the skin of my mind's particular concept of an idealized angel or some such perfect being. That's the power of fantasy.
The simulation + empathy model could also explain why we like doing nice things for each other. I want to give you positive experiences so that I can simulate you enjoying them, and then enjoy my empathetic kickback. "Just seeing the look on their faces makes it all worth it."
It can explain why real love requires time, but why the real measure is knowledge. We have to be able to simulate high-fidelity models of each other.
It can clarify the line between meaningful and meaningless sex. Meaningless sex is that without intimacy, that is, sex during which your mind is a black box to me, and I cannot accurately simulate how you're experiencing things. Alternatively, I might desire to hear your thoughts or voice, to see your reactions. I want to have sex with people whose minds I know in great detail. All this that I might receive and process information about my partner's mind, model it, and then get a kickback from empathizing with their pleasure. A cheap shortcut might be to project an imaginary detailed mind onto a sex partner and pretend that the partner is experiencing what the imaginary mind is (being simulated as feeling).
I said before that I was probably describing intimacy more than love. Intimacy + something negative = archfoes, while intimacy combined with something positive might equal true love. I'm not sure what those negative and positive things might be, though.