Grandparents can have visitation rights under a possession order but that does not sound like your issue. It doesn't matter that the mother will allow you to see the children but not the father. His rights relate specifically to the possession order.
I agree with Mr. Kielich. If there is a order in place and the mother is violating it, then your son needs to seek an enforcement of his visitation. If there is not an order in place, he needs to file suit so he can exercise his visitation.
Disclaimer: Attorney Stevens can be contacted for a consultation at 888-908-6296 or email@example.com. The answer provided is for informational purposes only. It should not be relied upon as specific legal advice and it does not create an attorney-client relationship. Information should not be acted upon without seeking professional legal counsel.
Sign up to receive a 3-part series of useful information and advice about child custody law.