This 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, 23:184.)
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.)