my whole family does this. it drives me nuts. i've noticed it for a long time. i've told my T's for years that even my brother can't maintain his own style, he dresses like his girlfriends (not in dresses!). I have a cousin who is a very funny impressionist. I do it too, I automatically mimic the speech pattern of whomever I am speaking with. I'm 60 and while I have a strong sense of self, it is not well integrated - I am more of an imaginary friend to myself.