What does living in captivity mean in the Book of Ether? How can men live in captivity and still sire children and raise up armies? Also, what set of rules do the Jaredites follow? They lived before the Law of Moses.
The Jaredites began as a very righteous people. The faith of the brother of Jared, Mahonri Moriancumr, was so great that he actually saw the Lord and conversed with him. So I imagine that the initial Jaredites would be living a higher law than the law of Moses, perhaps similar to the law given to Enoch and his people.
The details of the captivity of the Jaredite kings are not given in the Book of Ether. But it is easy to imagine that such captivity was not isolation in a dungeon, but rather a restriction from exercising rule, and permission to live with family members.
The captivity of the last Inca king, Atahuallpa, by the Spaniards could be a comparable example. Although he was taken prisoner by the Spaniards, and condemned to death, he was allowed to manage the affairs of his kingdom from prison, with a retinue of his subjects permitted access to him to convey his orders to his people.