you don't tell because
A) frightened, both of what's happening and what could happen if you tell
B) don't want anyone to be disappointed/ashamed/disgusted with you
C) they love you, don't they? This must be normal, right? they tell you they love you even when their hands are snaking up you and their breath is in your face, but then they tell you no one will believe you. They treat you more favourably to keep you quiet. You know its not normal deep down because nothing normal makes you feel so dirty inside and out
D) When you shy away from them in a family room, you're the one being told that's not nice - all they want is a hug, be a good girl and hug them - so you do. But they don't want to hug you really - they want to control you, remind you that they are there, watching - always. So don't tell.
E) Mam knows, so it's OK, right?
It's a mixture of a lot of things.
ime and moo