I don't think there's anything literally genetic about it, but I don't think it's your choice at all
for example, I don't remember ever deciding that I wanted to like richard. for that matter, I grew up being taught, and thinking for quite a bit of my early life, that homoloveuality was a sin, and would get you straight into hell. so it wasn't any kind of choice, I don't even know why I ended up this way.
in my opinion, people saying it's a choice is actually rather offensive