2 Nephi 1:28 says, "And now my son, Laman, and also Lemuel and Sam, and also my sons who are the sons of Ishmael, behold, if ye will hearken unto the voice of Nephi ye shall not perish. And if ye will hearken unto him I leave unto you a blessing, yea, even my first blessing."
At first, Lehi speaks to Laman, Lemuel, Sam, and the sons of Ishmael, and tells them that their blessing is contingent on them (ye) obeying Nephi. Notice that Lehi doesn’t include Zoram, Jacob, or Joseph in this contingency. The word "you" in the subsequent statement, "I leave unto you a blessing," can be read as a singular pronoun, addressing Laman, who would in the case of their obedience be entitled to Lehi’s "first blessing" and thus he could claim the power and privilege of being Lehi’s first son, the son who was presumably redeemed as an infant by Lehi in the temple. I assume that this would mean that Laman would receive a double portion of Lehi’s estate (twice as much as each of the other sons receive, as mentioned in Deuteronomy 22:17).
But if Laman and those others (note the plural "ye") do not hearken unto Nephi, Laman will lose that blessing and Nephi will step into that position. As Lehi continued in 2 Nephi 1:29, "But if ye will not hearken unto him I take away my first blessing, yea, even my blessing, and it shall rest upon him." Thus, the right of leadership would be taken away if Laman and the others do not hearken unto Nephi. At that point, Nephi would become Lehi’s primary successor.
The Lord had promised Nephi that he would be the teacher and leader in the event of the brothers’ iniquity (1 Nephi 2:21–22; cf. 3:29), and Lehi arranged his estate accordingly. Thus, Lehi provided that all could receive the blessings of prosperity and peace, if they would obey the commandments of God, the operation of religious laws, and the interpretation of scripture, as Nephi shall teach.
Lehi wanted his children to be in harmony, so he left them, as much as possible, in a position of equality. To compensate for the legal requirement that Laman receive the double portion, Lehi provided that Sam’s portion would be combined into Nephi’s: "thy seed shall be numbered with [Nephi’s] seed" (4:11). Lehi’s division of his estate was his final, creative effort to keep his family together in righteousness. Unfortunately, his plan did not last for long.