Narrative/Redaction: This verse adds important information, but it is chronologically misplaced. I hypothesize that Nephi adds the information here because the time in the wilderness did not advance Nephi’s spiritual story. Nevertheless, as he begins to relate the next significant spiritual occurrence, Nephi adds an important fact omitted up to this point. It is almost as if, remembering the departure, he realizes that these two brothers have not made their appearance on the scene. He corrects that oversight, then continues the portion of the narrative that interests him.
Culture: The narrative contains no details of these brothers’ births except that they occurred during the eight-year wanderings in the wilderness and that Joseph is younger than Jacob.
The names they are given are probably related directly to brass plates. With the acquisition of the brass plates, Lehi had newly refreshed his memory about his family history.
[He] also found upon the plates of brass a genealogy of his fathers; wherefore he knew that he was a descendant of Joseph… the son of Jacob, who was sold into Egypt, and who was preserved by the hand of the Lord, that he might preserve his father, Jacob, and all his household from perishing with famine.
And they were also led out of captivity and out of the land of Egypt, by that same God who had preserved them.
And now when my father saw all these things, he was filled with the Spirit, and began to prophesy concerning his seed. (1 Ne. 5:14–15, 17)
This experience tied together past and future, progenitors and progeny. By naming his sons Jacob and Joseph, Lehi commemorates the two most important names in his lineage. This gives us one interesting anomaly. The more important and immediate ancestor is Joseph. We have seen an emphasis on the story of Joseph in Nephi’s narration of events. (See section on Nephi as Joseph of Egypt in 1 Nephi, Part 1: Context, Chapter 2, “Introduction to 1 Nephi.”) I speculate that the naming order of the two sons suggests that they might have been twins. Lehi would not have known (short of direct revelation) that he would have two more sons, and we would therefore suspect that he would use the more significant name of Joseph for the firstborn son of the two. However, that is not the case. While this is the only indication that they might have been twins, it does explain the reason that Jacob was used for the older child. Lehi would have known he had two sons to name only if they were twins.