Lehi and Sariah had two more sons (and possibly at least one other unnamed daughter) during their eight-year sojourn in the wilderness. The names they chose for their boys are intriguing. Considering that this is a time when it seems pretty clear that Laman and Lemuel have squandered their birthright as the eldest sons, the parents are aware that there’s already a pattern in the family of younger sons subverting the usual order because of their greater degree of righteousness. So it’s certainly no accident that these two new boys are named Joseph (after the next-to-youngest son of Jacob, who ruled over all of his brothers because of his spiritual vision—despite their attempt to murder him) and Jacob (the younger twin brother of Esau, who disguised himself as his older brother in order to fool his father Isaac into giving him the blessing expected for older sons). In short, the Book of Mormon’s Jacob and Joseph are intended as spiritual replacements for older brothers who lost their way.
What’s more, the sudden appearance of Jacob and Joseph raises an important question: why are we only hearing about these new sons now, rather than on the occasion of their births somewhere in the wilderness narrative? Perhaps that’s because history is about to repeat itself in a way that the Joseph of the book of Genesis would have understood all too well: an attempted fratricide.
As Grant Hardy points out, another intriguing aspect of this section is the relative invisibility of the young brother Joseph in the rest of the Book of Mormon, where he does not feature prominently.