Peter Griffin
Peter always believed his full name was Peter Löwenbräu Griffin, however, later in the show, he finds out his actual full name is Justin Peter Griffin, and that he was born in Mexico. He also used to believe that Francis Griffin was his father, however, when Peter visited his father on his deathbed, he and his mother would reveal that his real father is an Irishman called Mickey McFinnigan, whom his mother met while she was in Ireland.