Utah Code Ann. § 76-7-102
(1) As used in this section:
(b) "Related person" means a person related to the provider or actor as an ancestor, descendant, brother, sister, uncle, aunt, nephew, niece, or first cousin, and includes:
(2)
(a) An actor is guilty of incest when, under circumstances not amounting to rape, rape of a child, or aggravated sexual assault, the actor knowingly and intentionally:
(b) Conduct referred to under Subsection (2)(a) is:
(iv) a woman 18 years of age or older who: