Internet Movie Database (http://us.imdb.com) is a treasure trove of
information about films and filmmakers. But if you ask it for Philip
Ahn’s filmography, you'll be told that he is sometimes credited
as Philson Ahn. Don't believe it.
Philson Ahn was
Philip Ahn’s younger brother and had a brief film career, mostly
in the late 1930s, before deciding to study engineering. Perhaps his
most often seen performances were as Prince Tallen in the twelve-episode
serial Buck Rogers with Larry (Buster) Crabbe. His other screen
appearances included small roles in The Good Earth (1937),
Disputed Passage (1939), Panama Patrol (1939), Barricade
(1939), and Island of Lost Men (1939). Perhaps the confusion
arises because Philip also appeared in these same films. Philson Ahn
died in May 2001.
Ralph Ahn, the
youngest of the three brothers, is also a film and television actor.
He appeared in a least one film with Philip, Confessions of an
Opium Eater (1962). You can check his other credits in the Internet