Nimrah was a son of Akish, the Jaredite king who had seized the throne by conspiracy and murder. Akish gained power through a secret combination that overthrew Omer, after which Jared was anointed king and gave Akish his daughter to wife; Akish then had Jared, his father-in-law, beheaded on his throne and reigned in his stead (Ether 9:1-6). Akish later grew jealous of one of his sons, shut him in prison, and kept him with little or no food until he died (Ether 9:7).
That son was Nimrah’s brother. Nimrah was angry with his father over the killing (Ether 9:8). He gathered a small number of men, fled the land, and went to live with Omer, the deposed king (Ether 9:9). War later broke out between Akish and his other sons and lasted many years, destroying nearly all the people of the kingdom except thirty souls and those who had fled with the house of Omer (Ether 9:12). The record gives no further account of Nimrah after he joined Omer.