Thaddeus had a sister, Hepzibah, who later married one of the members of that gang. In 1875, he had swindled the Parker family out of their property, and 116 years later, Biff Tannen claimed to have inherited the land from Thaddeus. Thaddeus also appeared to have trouble spelling. When using Marty's back to sign his name with an invisible ink pen he claimed to "Forgot to dot the I". When Marty said there wasn't an I in Thaddeus, Thaddeus noted "There is now."