Ohio Rev. Code § 5309.10: Assent by spouse.

If the application to register the title to land or to any interest in land is made by a married person, the spouse of that person shall signify the spouse's assent to the registration as prayed for by endorsement on the application acknowledged as a deed, or by a separate instrument so acknowledged and filed with the application. If the spouses are separated and living apart, or either one refuses to consent to the application of the other, the assent of the nonapplicant spouse is not necessary, and in that case the nonapplicant spouse shall be treated and named as a party defendant to the application.