His father was thumped in the U.S. Senate race, but Democrat Mike Slattery won a seat in the Kansas House.
The son, from the Kansas City suburb of Mission, unseated freshman Republican Rep. Ronnie Metsker, of Overland Park.
Results from Tuesday's election showed the younger Slattery with 55 percent of the vote in the 24th District.
Mike Slattery is a 26-year-old construction projects manager. His father, Jim Slattery, also was in his 20s when he won a Kansas House seat in the 1970s.
The elder Slattery also served 12 years in Congress before an unsuccessful run for governor in 1994, which pushed him into a career as a Washington lobbyist.
The father received 37 percent of the vote against Republican Sen. Pat Roberts.