Ohio Rev. Code Ann. § 3101.01
(A) Male persons of the age of eighteen years, and female persons of the age of sixteen years, not nearer of kin than second cousins, and not having a husband or wife living, may be joined in marriage. A marriage may only be entered into by one man and one woman. A minor shall first obtain the consent of the minor's parents, surviving parent, parent who is designated the residential parent and legal custodian of the minor by a court of competent jurisdiction, guardian, or any one of the following who has been awarded permanent custody of the minor by a court exercising juvenile jurisdiction:
(C)
(3) The recognition or extension by the state of the specific statutory benefits of a legal marriage to nonmarital relationships between persons of the same sex or different sexes is against the strong public policy of this state. Any public act, record, or judicial proceeding of this state, as defined in section 9.82 of the Revised Code, that extends the specific statutory benefits of legal marriage to nonmarital relationships between persons of the same sex or different sexes is void ab initio. Nothing in division (C)(3) of this section shall be construed to do either of the following: