Estate Law Questions? Ask an Estate Lawyer.
I will try and help. "Knowing"he is your father is not likely sufficient if there is a question, and even if you are, if he has a will, and you are not included, then you will get nothing and there is nothing you can do about it. Frankly, since he wife is still alive, you are probably premature in that in most cases the estate would go to his wife.
My suggestion it to inquire of your sister / siblings as to the status of the estate. If your father wife was not your mother, and there is not a will that includes you, then you are likely due very little if anything.
I know this is not what you want to hear, but I hope it helps.