[If] a woman [was] awaiting her yavam, and his brother then betrothed her sister, it was said in the name of R' Yehudah [ben Beseira]: We tell him, “Wait until your oldest brother acts!” [If] his brother performed chalitzah with her or married her, he may consummate the marriage with his wife. [If] the yevamah died, he may consummate the marriage with his wife. [If] the yavam died, [however,] he must discharge his wife with a bill of divorce, and his brother's wife with chalitzah.