Essentially, for years, I did what you did, trying to keep that relationship alive because it's the right thing to do, isn't it?!  Meanwhile, I always questioned why I felt the way I felt and why my instinct was telling me to run away.... which is exactly what I did a few years ago.   I think at the end of the day,  you need to take care of yourself and do what feels right and you can create your own family, based on valued relationships with friends.  Sharing the same blood doesn't guarantee love, only relationships based on respect and appreciation do!  Take care.