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The 26-year-old's victory made him the first player from Monaco to win an ATP singles title and set a record as the lowest-ranked player to triumph at an ATP Masters 1000 event.

The victorious Vacherot was overwhelmed with emotion, before sharing a heartfelt embrace with his older cousin Rinderknech, 30.

Vacherot had earned around a $920,000 in career prize money to this point, but lifting the trophy in Shanghai will see him pocket almost $2 million.

Vacherot's remarkable run to the title also means he is now ranked No.40 in the world while Rinderknech, ranked No.54, is set to rise inside the top 40.

"I'm just all like, crying, it's just, it's unreal what just happened. I have no idea what's happening right now, I'm not in a dream, it's just crazy. I'm just so happy of my performance these past two weeks," Vacherot said.

"I think there's just two winners today, one family that won, and I think for the sport of tennis, this story is just unreal.

"I wish there could be two winners, but unfortunately there's only one, and for myself, I'm really happy that it's me."

The cousins had given fans plenty to cheer about in the previous round – Vacherot stunning record 24-times grand slam champion Novak Djokovic and Rinderknech overcoming 2021 US Open winner Daniil Medvedev.

With Swiss maestro and former champion Roger Federer watching from the stands, Rinderknech broke first to lead 2-1 in the opening set, capitalising on a flurry of unforced errors from Vacherot.

The momentum continued to flow Rinderknech's way as he covered the court with impressive athleticism, racing to a 3-1 lead before extending it to 4-2.

Vacherot mounted a spirited fightback to narrow the gap to 5-4, but Rinderknech held his nerve to stave off his cousin's comeback attempt and seal the first set in 41 minutes.

In a tight second set, momentum swung back and forth with the duo locked at 3-3 before Vacherot crunched a backhand winner to break Rinderknech and surge ahead 5-3, keeping his cool to force a decider.

Vacherot came alive in the third set, breaking early to establish a 2-0 lead.

Although Rinderknech reduced the deficit to 3-2, he required a medical timeout to treat his back. Vacherot pressed on, sealing victory with a forehand winner down the line.

"That it's the guy that I've been training with in Texas A&M [University], that I've been growing up with on vacation and everything," Vacherot said.

"It was really tough, he did a better job than me in the first set.

"And yeah, just find a way to turn that around and then make the match a little bit myself towards the end."