I must say, I was not able to cross my legs until I was on hormones for a good month or so, I was relatively flexible, my problem was my legs kept going "dead"
After hormones for a while, I am now able to comfortably cross my legs, and sit with them together, even some other things that I used to not be able to do, such as sitting cross legged, or tucking my knees up under my chin.
I don't know, Maybe I am a lucky freak or something, because it seems, my pelvis is kind of wide, I can actually tuck a full size drinking glass between my legs, and cross them with no pain or anything. *has hips*