SHANGHAI, China (AFP) — World No. 204 Valentin Vacherot said he was in shock after beating his cousin Arthur Rinderknech 4-6, 6-3, 6-3 to win the Shanghai Masters late Sunday to become the lowest-ranked player to win an ATP 1000 tournament.

The unlikely all-family final between the 54th-ranked Frenchman Rinderknech and Vacherot, from Monaco, was described by the latter's coach and half-brother Benjamin Balleret as a "fairytale."

It was just the third ATP Masters 1000 final in history to feature two unseeded players.

"I don't even understand why I'm sitting here right now," the 26-year-old Vacherot said at the winner's press conference.

"It's crazy. I think I'm going to start realizing in the next few days, but right now, I just want to enjoy the moment."

Vacherot landed in Shanghai on a "little bit of a gamble."

He was on the alternate list for the tournament — meaning he wasn't even certain to take part — and found out just over a day before the qualifying rounds that he would play.

The performance that followed will propel the Monegasque from 204 to 40 in the rankings, according to the ATP website.

"The challenges were just everywhere," he said, and his current situation was "surreal."

On their way to the final, Rinderknech took out world number three Alexander Zverev and former US Open champion Daniil Medvedev.

Vacherot ended 24-time Grand Slam champion Novak Djokovic's chances of a fifth Shanghai title in the semi-finals as well as defeating world No. 11 Holger Rune.

Vacherot admitted having to face his cousin in the final was "not easy... to deal with."

Rinderknech broke Vacherot's serve with a backhand in the third game and it was enough for the 30-year-old to claim the opening set.

Watched on by Vacherot's idol Roger Federer, neither player was able to make headway early in the second.

Rinderknech faced a break point in the eighth game and saved with an ace.

He found himself on the brink again after an unforced error, and Vacherot did not miss his chance this time to force a decider.

The third set went off with a bang, with Vacherot snatching a break in the first game.

Vacherot looked increasingly dangerous as Rinderknech, seemingly flagging in the humidity, scrambled to save multiple break points in both the third and fifth games.

The Frenchman received treatment on his back after the fifth game, having almost been broken four times.

The partial revival that followed made for some tense rallies that energized the crowd, but Vacherot broke again at 5-3 to seal the title, doubling over in disbelief.

Coach Balleret said that in the second half of the match "the magic" happened.

"(I've seen him before) in this state of mind, of physical beast," he said of Vacherot.

"But to do it on the center court of Shanghai in the final against his cousin, it's another thing."

Rinderknech said after his semifinal that there would be "two winners" on Sunday whatever happened.

The two sat side-by-side, Rinderknech's arm around Vacherot's shoulder, as they waited for the trophy ceremony to begin — and were in tears during it.

Congratulating Vacherot and Balleret, Rinderknech joked: "Two cousins are stronger than one."

"I gave my everything, I couldn't have done more, but you deserve it so much, I'm so happy for you," he said, in a voice that cracked with emotion multiple times.

"I hope there will be more to come, it's only the beginning."

"Unfortunately, there was one winner, but probably one family won," Vacherot said.

"And the sport of tennis won as well, because the story we just wrote is amazing."