my dad

Have you asked your mom why she does not want you to contact him? Have you had a conversation with her, telling her why you feel the need to contact him and then really listening to her reasons for not wanting you to contact him?

But if you know his name and where he lives, I would think contacting him would not be difficult.

Did you your mom? What she said? Find some old stuff in home which is related to your dad and try to ask some questions about him.