Legal Question in Family Law in California

If he dies without a will, you have a good chance of being entitled to a share of the estate, IF you can prove you're his child. If he dies with a will, and follows the appropriate legal formalities, he may be able to leave you out of the will no matter what. That's a complicated question that is not answered the same in every state, so the state he made his will in and the state he dies in will affect what law applies. Again depending on the state, you may also have a right to back child support.

None of these questions can be answered with any certainty, however, without a thorough review of the facts and then legal research into the applicable law of the state(s) that have jurisdiction. Of course it's all moot if you can't prove he's your father, so that's the starting point.