Whywould anyone willingly go away with someone who abused them?

My father always abused me sexually as a child. It was my adoptive father, so I never really had a close "bond" to him anyways, but that didn't help. He ended up in jail for it, but was let out for good behior and my mother took him back. To this day he still abuses her (I live with my BF) and she just takes it. She works and could easily afford to leave, but she never actually does. I believe tat when someone ells you they love you, and you get close to them, it's VERY hard to let go, and scary to think that maybe this person isn't the prince charming he seems. My mom only had one serious bf before my father, and they have been married for over 20 years, so she never relly knew anything else.Your little siblings knew his as their father from day one, so no matter if he hit them or not, he is still the closest thing to "love" they have ever had. I am sure they are miserable, but they honestly don't know better. Someday, they will hopefully meet someone special who treats them how they really deserve to be treated, and then they too will see your ex stepfather is a jack ***