Kesubos Chapter 10, Mishnah 2. This mishnah continues the discussion of the enactment of kesubas benin dichrin - one of the conditions of the kesubah, according to which a woman's sons inherit her kesubah. When a man was married to two women, and one wife's kesubah was larger than the other's, these sums are not divided equally like the rest of the estate; rather, the amount of each kesubah is set aside and given to that wife's sons. This enactment can create a difference even when the two kesubos are equal in amount: if one mother has more sons than the other, the share each son receives will differ.
The scope of the enactment and its conditions:
Our mishnah teaches that kesubas benin dichrin applies only when a sum remains available in the estate after the kesubos have been paid, a sum that can be divided equally - which is the inheritance prescribed by the Torah. By Torah law everything is divided equally, while dividing the estate according to kesubas benin dichrin is only a rabbinic enactment. The Sages therefore instituted this enactment only on condition that the Torah's ruling in the laws of inheritance, which divides the estate equally among the sons, not be uprooted entirely.
The wording of the mishnah:
"Mi shehayah nasui shtei nashim u'meisu" - a man who was married to two women, and both died in his lifetime. "V'achar kach meis" - and afterward the husband died as well. The orphans, the sons of the two wives, "mevakshin kesubas iman" - each group claims its mother's kesubah. "V'ein sham ela shtei kesubos" - the estate contains only enough to pay the two kesubos, and nothing remains to be divided equally among the sons.
The halachah in this case: "Cholkin b'shaveh" - the entire estate, including the kesubah amounts, is divided equally. For kesubas benin dichrin applies only when a portion of the estate remains that can be divided equally as the Torah rules; and once nothing remains, the enactment is not implemented at all, and we return to the default of the Torah's equal division.
"Hayah sham mosar dinar":
"Hayah sham mosar dinar" - at least a dinar remains in the estate, which can be divided equally. In such a case - "eilu notlin kesubas iman v'eilu notlin kesubas iman" - each group of sons collects its own mother's kesubah, since the law of the kesubah is rabbinic.
The claim of the orphans:
"Im amru yesomim: harei anu ma'alim al nichsei avinu yeser dinar, kedei sheyitlu kesubas iman" - the orphans, particularly those whose mother's kesubah is larger or whose group is smaller in number, argue: true, less than a dinar remains in the estate, but we are willing to value the remainder of the property as though it were a dinar, so that they will be able to collect their mother's kesubah.
"Ein shom'in lahem, ela shamin es hanechasim b'veis din" - we do not accept their claim; rather, the estate is formally appraised. If the appraisal comes to less than a dinar, the rabbinic law of the kesubah is not implemented, and everything is divided equally.
In summary: in this mishnah we learned that the enactment of kesubas benin dichrin applies only when a surplus of a dinar remains in the estate to be divided equally according to the Torah's law of inheritance. If the estate contains only enough for the two kesubos, everything is divided equally; if a surplus of a dinar remains, each group of sons takes its own mother's kesubah. Nor may the orphans decide on their own to value the remainder of the property as a dinar, for the property is appraised in beis din, and if it comes to less than a dinar, the enactment is void and the division is equal.