Biological father

If the will has already been probated--or more generally, his "estate" (or the assets, if any he left behind) has already been probated, even if there was no will--then it is too late to do anything: once an estate has been fully settled in probate, it cannot be opened up and revisited.
If probate has not been completed, as a biological child who would have the right to inherit if there was no will (under the rules for "intestate sucession," or who gets what when there is no will, which generally provide for inheritance to children), you would have sufficient "standing," or potential legal interest in the matter, to bring a legal action in which you would demand to see the will and get your share, if the will gives you anything...or get your appropriate share if there is no will. But you would have to bring a lawsuit to do this if the estate's "personal representative" (the executor or administrator) does not voluntarily cooperate. If you want to explore legal action, contact a probate attorney--this is not the kind of action that a non-lawyer can likely bring successfully.
Note that if there is a will and doesn't leave anything to any unnamed or identified children--e.g. every person who inherits under the will is specifically identified--you will not receive anything:  a will is enforced as written, so if the estate is left entirely to named persons, only they inherit under it, regardless of what everyone believes your father would have done had he known of you. When there is a will, only the plain terms of the will matter.