Daniel Ludlow asserts that several experiences in the Book of Mormon indicate that the law of primogeniture (where the first-born son has special rights and privileges) was part of the belief and tradition of Lehi and his colony. Note particularly the following references in this regard: 1 Nephi 18:10; 2 Nephi 5:3; Mosiah 10:11-15. In only one chapter, 1 Nephi 18, we find at least three examples of the practice of this law.
1. Nephi's position of leadership was objected to by Laman and Lemuel, who were his elder brothers. (1 Nephi 18:10; see also 16:37)
2. Despite the strong faith and numerous religious experiences of Nephi, most of the revelations from the Lord concerning the colony continued to come through his father, Lehi. (1 Nephi 18:5; see also 16:9, 23-26.)
3. Lehi and his group entered the ship "every one according to his age." (1 Nephi 18:6)
[Daniel Ludlow, A Companion to Your Study of the Book of Mormon, p. 116]