In the agreement, Marx agreed to name Crown Prince William as heir to the position of Emperor of Ohio, on the condition that upon the former's abdication, the title would be changed to Prince of Ohio and made the possession of the Crown Prince of North America. This was then followed up by Marx's announcement of abdication from the throne of Ohio.
The title of Prince of Ohio is entirely ceremonial, as the Crown Prince has no obligation to abide by the Universal Rights of Man, the highest code of ethics and law in the former Ohio Empire.
You can read the Unification Agreement here.