Bava Batra 158 - The House Collapsed On Mother and Son
Consider the case where a house collapsed on a son and his mother. Since it is not known who died first, the paternal brothers of the son claim that perhaps the mother died first, the son inherited her, and they should inherit him. The mother's relatives (for example, her paternal brothers) claim that perhaps the son died first, so he never inherited anything, and therefore they inherit the estate.
Unlike in the case of a father and son , here the claims of both sides are equally based on "perhaps", and therefore both Beit Shammai and Beit Hillel agree that they divide it.
Rabbi Akiva says that Beit Hillel and Beit Shammai argue in this case also, but Ben Azzai said to Rabbi Akiva, "We are in enough pain over what they disagree , and now you come to dispute a unanimous decision?"
Art: Van Gogh - Backyards of Old Houses in Antwerp in the Snow