Brother of Arthur Chesney.
Brother-in-law of Estelle Winwood.
Cousin of Cecil Kellaway.
Cousin, once removed of actor Bryan Kellaway.
Fought in the British army during World War I.
In a magazine interview in 1998, Joan Weldon revealed that during the shoot of Them! (1954), the temperature reached 110°F and both she and Gwenn were wearing wool clothing. It was even more insufferable for Gwenn, who struggled with advanced arthritis. Although unnoticeable to audiences, he was in pain and was helped off set by his valet, Ernest.
Minnie Horace Beatrice Terry, to whom Gwenn was briefly married, was a member of the Terry acting dynasty, and a niece of Ellen Terry.
To date (2011) only actor to win an Oscar for playing Santa Claus.