you can try to clear the misunderstandings an/or offer a better perspective to one and the other. he only thing is, if somebody is really not loving, respectful or honest, the other one may not feel like take the chance or another chance.
Like a husband between his mother and his wife sometimes, they should be no idea of competition and confrontation but some people really follow the archetype and battle it out all their lives.
The one thing you make sure of: don't get used as a weapon against any of them, don't get involve in their war. You may need to let go or reduce your relationship with one of them to avoid problems in your daily life.
I have tried to get my half brother and my other brothers and sisters to talk: I have been cast out by everybody...and the one I was trying to help don't even talk to me either now. Apparently that was the purpose.