SHELLEY — A 21-year-old man who had sexual relations with a young girl frequently from the time she was 13 to when he was caught three years later has been sentenced to 20 years in prison.

Arynn Millus will spend a minimum of five years in prison with an indeterminate time of 15 years held over him. He was credited 123 days for time already served in county jail.

Court documents show the 16-year-old victim told police the sexual abused started when she was 13 years old. Millus admitted to police he had been having sex with the victim one to two times a week for the last year until he was finally caught in late November 2017.

Documents show the victim’s 12-year-old sister was the one that caught Millus having sex with the victim.

The abuse was reported to a member of a Mormon Bishopric. The family told the ecclesiastical leader they wanted the matter handled within The Church of Jesus Christ of Latter-day Saints. However, the leader told the victim’s mother the matter could not be handled within their church, and he notified police of the abuse.

The victim’s father told police he was worried about what the incident was going to do to his marriage. When asked what he meant, the father reportedly explained he believed the victim’s mother was bullying the 12-year-old sister by telling her that none of this would have happened if she hadn’t spoken up about what she had seen.

When police initially confronted Millus about the sexual abuse he said the victim was making it up because he isn’t Mormon and talks bad about Mormons.

Police told him a rape kit came back positive. Millus said the victim must have gotten his semen from a towel or toilet seat. Documents show police kept pressing him until he admitted to having sex with the victim.

During a forensic interview with the victim, she told police Millus had been having sex with her every time they were alone since she was 13. The 12-year-old sister, during a similar interview, told police Millus had offered her money to have sexual relations with him.

Millus will be required to register as a sex offender and pay $4,045 in fines.