Responsa for Shevuot 93:8

Q. A was survived by his wife, a married daughter, and a single daughter. Subsequently the married daughter died and then her death was followed by that of her mother. The latter had not taken the required oath regarding her ketubah. The unmarried daughter took possession of A's entire estate; but, A's son-in-law demanded half of the estate on the grounds that his wife had been entitled to it, and that he was her rightful heir.
A. As long as A's widow did not take an oath regarding her ketubah, A's entire estate belonged to his two daughters. A's son-in-law, being his wife's rightful heir, is, therefore, entitled to half of A's estate.
This Responsum was addressed to Rabbi Menahem.
SOURCES: L. 226; Mord. Sheb. 780. Cf. Israel Bruno, Responsa 21.

Q. A, his four daughters, and his wife, were killed when the house they occupied collapsed. A's heirs claim that perhaps the wife died first and that therefore they now were the only heirs to A's estate. The wife's brothers, on the other hand, claim that perhaps the wife died last and that therefore they were entitled to her ketubah. Some Rabbis are of the opinion that the wife's heirs were entitled to one-twelfth of the estate; while other Rabbis, computing probabilities, believe that they were entitled to one thirty-second of the estate.
A. It is my humble opinion that the wife's heirs are entitled to one-half of the estate, because of the talmudic principle Kol Kavua kemahaze al mahaze domi, meaning: whenever an event is about to befall (or has befallen) one of a number of fixed persons or objects, each person or object has a fifty-fifty chance that the incident will befall (or has befallen) him or it. Therefore, legally, there is a fifty-fifty chance for each one of the six persons involved that he or she died last. Had the daughters been married and had their husbands appeared to demand their share, the estate would have had to be divided into six parts. But, since only two persons demand their share, the estate should be divided between the two. Although a woman has to take an oath before she is entitled to collect her ketubah, no such oath is required in this case since A died suddenly and we have no reason to suspect that before his death he had deposited with her valuables to be used in payment of her ketubah.
SOURCES: Cr. 172; L. 378; Mord. B. B. 638; Tesh. Maim. to Mishpatim, 5; Agudah B. B. 213; Asher, Responsa 84, 3. Cf. ibid. 85, 1; ibid. 86, 1; Maharil, Responsa 63; ibid. 169; Moses Minz, Responsa 96; Terumat Hadeshen 330.

Q. A lent money, on trust, to B who subsequently left for a distant country where he was robbed of all his possessions. Upon his return he settled with A for three halves (half-pounds, marks), and gave A a note of indebtedness in which no specific date of month or day, but the calendar year since the creation of the world appeared, and which contained a clause to the effect that A is to be believed without an oath should any litigation arise concerning this debt. After B's death his widow seized his property in payment of her ketubah, which property barely covered ten percent of her claim, without taking the usual oath required of a widow upon the collection of her ketubah. Ten years after the death of B's widow, A presented his note for collection and demanded the full amount from B's sons. The latter claimed that their father left them nothing, that they inherited valuables from their mother only, and that B had paid A part of the debt contained in the note. A single witness testified, and A himself finally admitted, that B had repaid one-sixth of the debt.
A. A controversy exists regarding the status of the property seized by a widow in payment of her ketubah, if the widow died before taking the required oath. Some are of the opinion that the entire property reverts to the husband's estate; while others hold that the part of such property which is valued at no more than half of the amount of the widow's ketubah remains part of the widow's estate, while anything above that amount reverts to the husband's estate. The latter opinion is accepted. Therefore, if B's sons take an oath that they inherited nothing from their father, they are free from any obligation to A. If, however, they are willing to repay their father's debt, they may demand that A take an oath as to the amount actually due him, since he has been proven to be untrustworthy.
SOURCES: Pr. 859.