Ohio Rev. Code § 3103.05: Contracts.

(A) A husband or wife may enter into any agreement or transaction with either of the following:

(1) The other spouse, subject to the general rules that control the actions of persons occupying the confidential relations with each other;

(2) With any other person, which either might if unmarried.

(B) An agreement under division (A)(1) of this section that alters the legal relations between the spouses shall comply with section 3103.061 of the Revised Code.