How long would you stay to help another family, when it's a toxic environment?

I have been out of service for almost 24 years (Oct 26 will be 24). When I got back to the states (left the states in 86 and returned in 09) I came across a family that I had know since childhood. One of the daughters had gotten with me on Face Book and we started talking and she told me she was going through a divorce that was dragging on and had no means to support her children ( 5). I wound up going to meet her and them and have now been here for 5 years. During this 5 years I have made it VERY clear that I will not become active with her as she is still married but will help her out. Also in this time I have become very bitter towards her 3 sons who have tried their very best to piss me off to the point where I will want to leave, this includes making false claims that I almost beat one to death and child protective services stepped in, The child wound up admitting that it was all just a lie and was just another attempt to get rid of me. I have kicked one out just shy of his being 18 for disrespect and am on the verge of doing the same to the next one and just enrolled the 3rd (15) into a military academy to turn his ass around. My dilemma is this: After so much friction I am torn on staying with this family or just walking away. They have absolutely no income , I finance the house , the cars, everything and know if I leave they will return to a life of poverty. I absolutely love the two girls (15 and 17) along with the mom, but as said all this crap with the boys has put a HUGE wedge between us. Any suggestions??I know it will in the end fall on my decision alone, I just am torn in what direction I need to travel. UPDATE!!!! I have asked them all to leave and have started rebuilding my life, I thank all of you who responded.. It helped me confirm what I already knew i needed to do.