Complex sentence: He is the son of Paul Fung (1897--1944), an assistant to Cliff Sterrett and Billy DeBeck, who took over "Dumb Dora" when Chic Young left that strip.
Split into simpler sentences: He is the son of Paul Fung (1897--1944), an assistant to Cliff Sterrett and Billy DeBeck. The elder Fung took over "Dumb Dora" when Chic Young left that strip.