(a) A person commits incest if he marries or engages in sexual intercourse with a person he knows to be, either legitimately or illegitimately:
(1) His ancestor or descendant by blood or adoption; or
(2) His brother or sister of the whole or half-blood or by adoption; or
(3) His stepchild or stepparent, while the marriage creating the relationship exists; or
(4) His aunt, uncle, nephew or niece of the whole or half-blood.
(b) A person shall not be convicted of incest or of an attempt to commit incest upon the uncorroborated testimony of the person with whom the offense is alleged to have been committed.
(c) Incest is a Class C felony.