I came up with three possibilities for the disappearance of his mom: (1) she died during childbirth, (2) she was sent away after he was born, or (3) she was killed after he was born.
As for his father's hatred towards him, I feel that it could be due to #1 or #2, or could be due him just being a dick and hating humans (even though he mated with one).
Idk tbh, but this story is goooooood.