Should I be the one to contact my exes side of the family?

My son’s father and I are no longer together and he has no contact with our son. Should it be my responsibility to contact his side of the family to spend time with or get to know our son? His family knows how to contact us but haven’t.

I say maybe reach out once. Throw the ball in their court. That is if y’all had a decent relationship. If y’all relationship was horrible I say they should reach out to you