"61 And again, as pertaining to the law of the priesthood—if any man espouse a virgin, and desire to espouse another, and the first give her consent, and if he espouse the second, and they are virgins, and have vowed to no other man, then is he justified; he cannot commit adultery for they are given unto him; for he cannot commit adultery with that that belongeth unto him and to no one else."
https://www.churchofjesuschrist.org/study/scriptures/dc-testament/dc/132?lang=eng
Ether's grandfather Moron had been king of the Jaredites. Moron was overthrown and "dwelt in captivity all the remainder of his days"
https://en.wikipedia.org/wiki/Ether_(Book_of_Mormon_prophet)
Moron