Ishmael and his family were brought down from Jerusalem by Nephi and his brothers, according to a divine command. (1 Ne. 7:2) Marriage for the purpose of raising up posterity "unto the Lord" was enjoined upon them as a sacred duty.
Ishmael had five daughters and two sons. During the journey from Jerusalem to the Valley of Lemuel, Laman and Lemuel opposed Nephi. They even bound him and plotted his death. Two of the daughters of Ishmael sided with Laman and his supporters. One daughter of Ishmael stood up valiantly for Nephi, and plead so sincerely for his righteous cause that he was set free. (I Nephi 7:19) Thus a line of cleavage was already drawn. In all probability, the two girls who had sided with Laman and Lemuel became their wives, while the valiant little girl, possibly the youngest of them, joined her hero in the sacred relationship contemplated. There were two girls left. Zoram, the servant of Laban, married the oldest daughter, and Sam presumably the remaining girl.