Hello Debbie,
There were four guys named Hugh Fullerton from South Belfast who signed the Ulster Covenant in 1912.
Hugh Fullerton, 68, Barkmore Street, Belfast
Hugh Fullerton, 115, Utility Street, Belfast
Hugh Fullerton, 68, Bankmore Street, Belfast
Fullerton Hugh 115 Utility Street Belfast: South
It looks as though these ones were not your Hugh ... I guess they were a father and son in each instance.
Chris