Not to be a hardass realist and not trying to upset you, but however horrible this situation is now I can almost guarantee it would get a thousand times worse if someone in the triangle were to die. If your grandmother were to die your aunt could very well inherit her share of the property and your parents could very well end up going from the frying pan into the fire and get legally entangled with your aunt, anyway. Or not, you just never know how things will work out. Your parents are in a rotten situation no matter what. It's rotten now in the present, and 20 years from now it could be just as rotten. The thing for them to consider is which rotten do they want to extricate themselves from and deal with - the rotten of the present which they know and can somewhat keep control over, or the rotten of the future and all of its unknown variables?