Ken Curtis was 28 in Rhythm Round-Up when he played the character 'Jimmy Benson'.
That was over 79 years ago in 1945.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 1991 he died aged 74, starring in 41 films in his career, 40 of those after Rhythm Round-Up was first released. If he were alive today he would be 107.
In Rhythm Round-Up, I think Ken Curtis looks: