Ind. Code § 35-46-1-3 – Incest

(a) A person eighteen (18) years of age or older who engages in sexual intercourse or other sexual conduct (as defined in IC 35-31.5-2-221.5 ) with another person, when the person knows that the other person is related to the person biologically as a parent, child, grandparent, grandchild, sibling, aunt, uncle, niece, or nephew, commits incest, a Level 5 felony. However, the offense is a Level 4 felony if the other person is less than sixteen (16) years of age.
(b) It is a defense that the accused person's otherwise incestuous relation with the other person was based on their marriage, if the marriage was valid where it was entered into.
As added by Acts 1976, P.L.148, SEC.6. Amended by Acts 1977, P.L.340, SEC.86; P.L.158-1987, SEC.5; P.L.79-1994, SEC.16; P.L.158-2013, SEC.549.