When I was fourteen, I decided (or, rather, admitted to myself) that I wanted to feel wanted by women - or at least, the girls my age. Sex was only one part of that. That desire has stayed, it's just that I later decided on top of that that I wanted to eventually have children too.
I'd almost like to say companionship too, because it seems like a charming and innocent answer, but honestly it's never been the deciding factor. There were long periods in my life where I, though as always still interested in having more friends, had enough companionship to at least satisfy me - and I was single. I feel like I could do with a couple of close friends now (in grad school, which is a bit lonelier than college), but they don't have to be female.