Well, I can understand Alejandro's reaction towards his mother , Hell! I would even curse them in front of them. That's natural.
But, I lack info, i.e., story from the parent's side, how and why they die, what was their reaction at the time of passing the curse to their own child, THEIR OWN MONOLOGUE would be way better for me to make my judgement regarding them.
I hope author would alleviate my concerns.