I assumed my mom would have tried to be more supportive when I first realized I was trans (until my brother brought a trans boyfriend home...) and I assumed my step-mom would have been more disapproving (even if I assumed she wouldn't express it much directly).
By the time I actually came out though, I suspected the biggest problem I'd have is I'd have to deal with my mom's dysphoria (egg?), and that turned out more true than I even expected.