By all accounts he could be a difficult person to be friends with. He admitted many times he let Stills, Nash ,and Young down on many occasions. He remained in contact with Stills but Nash and Young hadn't really spoken to him for quite some time. There are a couple of interviews with him where he goes into all of this. He hoped they would all reconcile but it never really happened and then he died.
There's a short interview with him just a few days before he died on you tube where he talks about it.