Vladimir Guerrero, Jr. topped his father and Shohei Ohtani with one swing on Monday.
Guerrero hit his Major-League-leading 45th home run as the Toronto Blue Jays beat the Tampa Bay Rays 8-1.
Facing Adam Conley in the sixth, Guerrero lined a 3-1 pitch down the left-field line, breaking a tie with Ohtani for most home runs in the Major Leagues.
With his homer, Guerrero also eclipsed the single-season high set by his dad with Montreal in 2000.