I knew a man who was the only member of his family to escape a house fire. He told me he lived with survivor guilt for years until he finally sought profession counseling. Part of his problem was that he felt like other members of the family deserved to live more than he did. He had lived a full life and was prepared to die, but his young children deserved a chance to experience more things life had to offer.
He really had a hard time coping with the guilt of survival. His counselor called it "survivor guilt syndrome", and diagnosed him with PTSD. He's getting better over time, but I can tell he's prone to beat himself up over the tragedy. I think a lot of survivors are in the same situation.