Felix Auger-Aliassime of Canada and Kylie McKenzie of Anthem, Ariz., completed stunning title marches on Sunday in the Eddie Herr International Championship in Bradenton, Fla.
Saving three match points, the sixth-seeded Auger-Aliassime edged No. 4 Alex De Minaur of Australia 6-3, 6-7 (6), 7-6 (3) in the boys 18s.
De Minaur, 16, served for the match at 5-4, 40-0 in the third set. Auger-Aliassime, 15, also survived three match points in his 2-6, 7-6 (8), 7-6 (2) victory over Alexandar Lazarov of Bulgaria in the third round.
The unseeded McKenzie outlasted No. 5 seed Tamara Zidansek, 17, of Slovenia 3-6, 6-3, 6-4 in the girls 18s.
McKenzie, 16, saved a match point in the third round and ousted No. 1 seed Dalma Galfi, the reigning U.S. Open girls champion from Hungary, in the semifinals.
In March at 14, Auger-Aliassime became the youngest player to qualify for a main draw in ATP Challenger history. He won the U.S. Open boys doubles title with countryman Denis Shapovalov in September and led Canada to its first Junior Davis Cup title the following month in Spain.
The Eddie Herr Championship is one of the most prestigious junior tournaments in the world. Past competitors include Roger Federer, Andy Roddick, David Nalbandian, Maria Sharapova, Jelena Jankovic and Ana Ivanovic.
Herr, the father of international junior tennis, died in 2000 at 93.
Many of the players in this year's Eddie Herr Championship will compete in this week's Orange Bowl, the most prestigious junior tournament in the world outside of the four Grand Slams, in Plantation, Fla.
Heavy rain postponed the start of main-draw singles in every age group.