I think (not absolutely sure) that for me there are several reasons why it's been easier (a lot easier) to separate from family than exes.
1. Family abused me from the day I was born (and even before that as I consider substance abuse (marijuana, cigarettes, alcohol) during pregnancy abuse), i.e. it went on considerably longer than the abuse of my exes... as I had to endure it the first 18 years of my life and had zero choice.
2. With family, as said, I had no choice. I don't feel guilty at all for being abused. I absolutely understand how they had the power and I had nothing. It is so clear to me that what my family did was dead-wrong, that I have no problem at all letting them go. I left them on all levels, even gave all my names up I was given after birth, and chose my own, officially. I have not been in contact with any abusive family members and have remained in touch only with one non-abusive one, my cousin.
What drives me nuts with exes is the fact that I do not have to choose them, but do choose them. That makes me feel responsible for my own actions, which I no doubt am responsible for. But despite 20 years of therapy and self-help CAN NOT (am not able to) make decisions about men that are not detrimental to me. Drives me nuts. For some reason I feel or seem to believe I do not deserve to leave them because I chose them in the first place. I sort-of "deserve" the treatment because it was my choice. And therapists etc. have it that as an adult you ARE able to choose. Well... sincerely... I am not. Hopefully not yet, but I feel like giving up.
I hope you will find your way out of the circle of abusive family. I have never regretted it and it has had such a positive impact on my life. Best wishes.