Incest is divided into two crimes. Incest, C.R.S. § 18-6-301, occurs when a person marries or subjects to sexual contact an ancestor, descendant, whole or half sibling, or an uncle aunt, niece or nephew of the whole blood. Incest is a class 4 felony. Aggravated incest, C.R.S. § 18-6-302, occurs when a person a) marries or subjects to sexual contact his or her natural child, stepchild or adopted child; or b) marries or subjects to sexual contact a descendant, whole or half sibling, aunt, uncle, niece or nephew who is under ten years old. Aggravated incest is a class 3 felony