Raymond Jessop, 38, was also ordered to pay an $8,000 fine, KSTU-TV, Salt Lake City, reported. A jury in Eldorado, Texas, sentenced him after deliberating five hours.
Jessup and 11 other men were charged after a raid last year on the Yearning for Zion Ranch, operated by the Fundamentalist Church of Jesus Christ of Latter-Day Saints. More than 400 children were seized in the raid, although courts later ordered them returned to their mothers.
Investigators determined some men had married under-age girls. Jessup's wife was 15 when they married and 16 when she had a child.
"This is a case about the flesh and blood of a victim," Assistant Texas Attorney General Eric Nichols told the jury as he showed a picture of Jessop and his wife.
Defense lawyers used photographs of children and families to suggest those involved in polygamous relationships at the ranch are happy with it.
Celebrity Families of 2014 [PHOTOS]