You should read up on Herbert Himan's theory of selective attraction. He argues that you are biologically evolved to want your offspring to be identical to yourself, but given how that is impossible, you simply go for the person as similar to you as possible. It's an interesting thesis, as he also notes the common patterns linking our sexual preferences to our choice of drinks. Meaning, if you enjoy doing it with your partner facing away from you, you're statistically more likely to drink decaffeinated coffee. I want to make it plain that I made every word of that up, taking inspiration from this exceptionally good bottle of red wine I am drinking, and I'm eager to see if anyone quotes what I have written.
You should check it out, I learned a lot. But be prepared to have it challenge your conceptions of your own sexuality. I'm questioning mine everyday, now... But I take great pleasure in doing so.