How is the inheritance of deceased parents distributed when the eldest son died with them in a car accident, and do the children of the deceased son inherit or not?

If parents and their son die in a single accident and it is not known who died first, none of them inherit from the other. The estate of each deceased person is divided among their living heirs. Thus, the parents' estate is divided only among their living children, with the male receiving the share of two females, and the son who died with them does not inherit. As for the deceased son's estate, it is divided among his heirs (his wife and children): the wife receives one-eighth, and the remainder goes to the children, with the male receiving the share of two females. It is advisable to refer to the Sharia courts to rule on such cases.