He never knew his brother TB Yevamot 17

With today’s daf TB Yevamot17 we begin the second chapter of our massekhet. The first Mishna of the first chapter enumerates 15 different ervot (ערוות) prohibited marriages that exempts her from yibum or halitza. One of them is a brother who wasn’t born at the same time his married brother died. Today’s daf describes how that could happen and how do we learn this halakha.

“MISHNA: Each of the women enumerated in the first chapter causes exemption from levirate marriage and ḥalitza for her rival wives. This is due to the close family relationship she has with her brother-in-law, making her forbidden to him. The single exception is the case explained in this mishna. What is the case of the wife of a brother with whom he did not coexist?  (אֵשֶׁת אָחִיו שֶׁלֹּא הָיָה בְּעוֹלָמוֹ)For example: If there were two brothers, and one of them died childless, and subsequently a brother of theirs was born, after which the second brother, the elder, took his deceased brother’s wife in levirate marriage, and then died as well. Consequently, two women require levirate marriage: The widow of the first brother who had been taken in levirate marriage by the second brother, and the widow of the second brother, the first widow’s rival wife. The first widow, who had been the wife of the first brother to die, goes out without any obligation to be taken in levirate marriage by the youngest brother who was born later, since she is the wife of a brother with whom he did not coexist. The first deceased brother never lived at the same time as the newly born brother. The second widow, who had been married to the second brother, is exempt due to her rival wife.” (Sefria.org translation)

Let me paint the scenario to make this concept easier. Reuvan and Shimon are brothers. Reuvan married Leah and Shimon married Rachel. Reuvan died without children. Shimon took Leah in a levirate marriage and then another brother was born and his name is Levi. Shimon now has two wives, Leah and Rachel, when Levi was born.

Shimon died without children and now both Leah and Rachel come before Levi as the surviving brother. Leah isn’t a candidate for yibum because Levi wasn’t alive during Reuvan’s lifetime. This is the case of “the wife of a brother with whom he did not coexist.” Because Rachel is a tzarat ervah, she is exempt from yibum and halitza.

The Gemara explains the verse what kind of brother is exempt from observing the mitzvah of yibum. “The Gemara turns from a review of the language used in the mishna to a discussion of the halakhot of a wife of a brother with whom one did not coexist. Where is it written that the mitzva of levirate marriage does not apply in the case of the wife of a brother with whom he did not coexist? Rav Yehuda said that Rav said: The verse states “If brothers dwell together and one of them dies” (Deuteronomy 25:5), meaning that they had a common dwelling together in the world. This excludes the wife of a brother with whom he did not coexist. Furthermore, it is derived: “Together” means that they were united together in an inheritance; i.e., they are united in that they inherit together. In other words, since property is inherited by sons from their father, it can be inferred that the verse is speaking specifically of brothers from the same father. This excludes his maternal half brother, with whom he is not united by inheritance, since only brothers who share the same father inherit from each other.” (Sefaria.org translation)