Charles Leslie Barnum was the son of Charles Knapp Barnum. According to the 1900 Census for Brooklyn, Kings County, New York, ED 383, sheet 5, he was born in June 1888.
He married Eleanor Williams and they had two children; Charles Knapp Barnum born about 1913 and Eleanor A. Barnum born about 1917.
Sources:
1920 Census: Richmond, Richmond County, New York, ED 1554, sheet 9B
1930 Census: Pleasantville, Westchester County, New York, ED 190, sheet 10B, lines 97-100.