Boyfriend's cat sleeps on my legs at night. Is this a sign of affection?

Hi all!

My boyfriend and I have been living together for about a year and a half now. When his cat is in the bedroom at night, he always ends up sleeping on my legs. It's cute, but it makes it hard to move around at night. During the day the cat is much more affectionate to my boyfriend than me.

Does the cat sleep on my legs as a sign of affection, or is it a sign of dominance? I don't really care either way, but it's something I've always wondered.

Thanks for any input!