When Nephi fled from Laman and Lemuel into the wilderness, he mentions that among the people he took with him were "my sisters" (2 Nephi 5:6). How many sisters did Nephi have?
Option #1:
According to Sidney Sperry, the fact that "sisters" is mentioned means that at least two sisters went with Nephi into the wilderness. Were these sisters the elder daughters of Lehi who had married Ishmael's sons? It would seem highly improbable. For we remember that Lehi's married daughters were among those who had rebelled against the faithful members of Nephi's party when they were bringing Ishmael's family from Jerusalem (1 Nephi 7:6). It would be hard to believe that these rebellious daughters of Lehi would leave their husbands and children and desert to Nephi's camp without his mentioning the fact. [Sidney Sperry, Answers to Book of Mormon Questions, p. 11]
According to Daniel Ludlow, the reference to "my sisters" here in 2 Nephi 5:6 is the only specific reference in the Book of Mormon that Nephi had sisters as well as brothers. How many sisters there were, whether they were older or younger than Nephi, or what their names may have been are questions not answered in our present Book of Mormon.
However, the following statement by Erastus Snow may provide information on some of the sisters of Nephi:
"The prophet Joseph informed us that the record of Lehi was contained on the 116 pages that were first translated and subsequently stolen, and of which an abridgment is given us in the first Book of Nephi, which is the record of Nephi individually, he himself being of the lineage of Manasseh; but that Ishmael was of the lineage of Ephraim, and that his sons married into Lehi's family, and Lehi's sons married Ishmael's daughters" (Journal of Discourses, Vol. 23, p. 184).
The words that Ishmael's sons "married into Lehi's family" would seem to indicate that the two sons of Ishmael (see 1 Nephi 7:6) were married to Lehi's daughters (and thus to two of the sisters of Nephi).
However, the sisters referred to in 2 Nephi 5:6 are evidently still other sisters, because the sisters mentioned here follow Nephi when the schism with Laman occurs, whereas the sisters of Nephi who were married to the sons of Ishmael evidently stayed with their husbands and joined with Laman (see Alma 3:7 and 47:35). [Daniel Ludlow, A Companion to Your Study of the Book of Mormon, p. 131]
Option #2:
According to John Sorenson, the two (or more) daughters of Lehi and Sariah are presumed, on the basis of Erastus Snow's statement, to have become wives of Ishmael's sons. These sisters of Nephi were apparently (unmarried) minors at the beginning of the account, otherwise there would be no way to place them in Sariah's birth history. [John Welch's assumption that Nephi was Lehi's sixth child (two sisters older than he) is highly unlikely, for that would stretch out Sariah's fertility history to an unbelievable and unnecessary length.] I suppose that one was around twelve and the other around nine (when Lehi left Jerusalem). When they arrived in Bountiful they would have been twenty and seventeen.
It is logical that in the intimate circumstances of the camp, youths approaching sexual maturity would be in a socially awkward position. Likely, the adult role of wife would be arranged for the two daughters as soon as feasible, say around age sixteen for each in turn, but whom would they marry? The sons of Ishmael alone seem of an age to be possible husbands. Lehi's first daughter may then have become the second wife of Ishmael's first son at about the time they were in Nahom. The second daughter could have become the second wife to Ishmael's second son no later than the time the party reached Bountiful. [John Sorenson, "The Composition of Lehi's Family", in By Study and Also by Faith, Vol 2, p. 190]