Szep was a strong opponent of the Vietnam War and his cartoons on Edward King, the governor of Massachusetts, resulted in his being sued for libel. In 1987, a court dismissed King's suit. His work is currently syndicated by Creators Syndicate. He has a daughter Amy (artist, born 1967). His son, Jason Szep (born 1969), a Reuters journalist, also won a Sigma Delta Chi Award (2007) and a Pulitzer Prize for International Reporting (2014). Jason Szep, formerly Southeast Asia Bureau Chief at Reuters, is now International Affairs Editor for Reuters, based in Washington.
In 2010, a putter discarded by Szep and sold at a discount golf store was bought for $39 by Jim Furyk, who won the $11 million FedEx Cup tournament with it.