Your needs will be best met by retaining local experienced family law counsel. Here on the Avvo Q&A the caring and knowledgeable attorneys tat volunteer can provide accurate information about the law and legal procedure, but this format is ill-suited to advising strategy in a particular case.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.
Generally speaking, you don't have rights as a grandparent. If he wants to exercise his rights as a father, he needs to file a paternity suit and establish a time sharing schedule. When he has time sharing with his son, he can allow you to see your grandson. Ms. Sinclair is correct that you should retain an attorney to review the facts of your case and help you sort out the particulars.
***Please be sure to mark if you find the answer "helpful" or a "best" answer. Thank you! I hope this helps. ******