Laman and Lemuel, The Book of Mormon

Laman and Lemuel were two of Nephi's three older brothers. The scriptures almost always link the two, and so lacking other material, we have no way of seeing them separately. We meet them along with the rest of Lehi's family in the earliest chapters of the Book of Mormon. They appear to be around twenty years old, without families of their own at the start.
It should be noted here that the record we have was written by Nephi, whose accounts don't include the good qualities of these brothers, whatever they may have been, but concentrate on their relationship with Nephi, which is often hostile and near violent owing to (according to Nephi) their jealousy of his status as future family leader and a person of spiritual authority.
When it becomes evident that Lehi and family will never return to Jerusalem to live, and that their future is quite uncertain, Lehi's sons are obliged to consider whether all this is necessary and good for them all. Nephi makes the question a matter of prayer, and receives an answer that puts him solidly with his father, wherever the family might go.
Laman and Lemuel are slightly older, and much more worldly. They had counted, no doubt, on joining their father's trading business at  some point, and enjoying everything that would go with what passed for the ancient "good life". They not only couldn't see the merit in leaving, they couldn't generate enough faith in their father to believe he had a plan, either.
It was not as though they never had the chance to change their minds. The scripture records that on several occasions the two older brothers saw visions, heard voices, witnessed miracles and were instructed properly in being faithful sons. But some of this instruction came from Nephi, which would have tainted it in the minds of his brothers.
The rift in the family never is healed. The two older brothers and their families are estranged from the others, and, following Lehi's passing, they devolve into a separate people, coming from the same gene pool, but passing on their personal enmity to succeeding generations who treat it as a way of life. It is from the oldest brother, Laman, that the Lamanites get their name. Through much of the Book of Mormon, the conflict overlaying the conflict we all experience between good and evil is that of the Nephites and their lethal sworn enemies, the Lamanites.
LIke Miss Haversham of Dickens "Great Expectations", jilted on what was supposed to be her wedding day many years before and feeling the pain of that day so completely that the wedding banquet is left to rot at the great table where it was to be served, these two brothers just couldn't get past the loss of wht they thought their lives would be like. Unwilling to blame themselves for this all too human tendency, they were ultimately willing to see their entire progeny kept in spiritual darkness, wasting their lives on an incorrect premise.