I never knew my father either. He did leave my mom when I was 2 and she was 8 mths pregnant with my brother. He literally went to the store for cigarettes and never came back. I did however grow up having a relationship with his mom (my grandmother) and his brother (my uncle and aunt).When my grandmother died 10 years ago (I was 30), he called me. Wham!!!!!! Out of respect, I tallked to him. He even came to visit us from California. He did not stay at my house. To be honest, I really had NO feelings either way. I never longed for my father or hated him. He died a couple of years later and I know that it is terrible, but I still had no feelings about it. He had supposedly changed and turned his life around. His was a Vietnam Vet and when he came back he started drinking and using drugs. I suppose I was just letting him get some kind of fullfillment before he died since he made the effort to call. .
I guess this does not help , but I just thought I would share my story. He was able to share his side of the story without trying to jusify it. I believe it was genuine. So maybe just let him talk and tell you his side of the story.