Non adopted step children are "generally" not legal children. Unless a will left them something by name (which sure can still be done) they have no more right then I would to a claim. Also, if the decedent died intestate the laws of intestste succession determines their "heirs at law" and step children are NOT heirs at law and dont "usually" take.
Still, not having read the will nor researched your states laws my albeit still professional legal opinion is worth just what you paid NOTHING
Remember, "A living person has no heirs"