Former Barcelona forward Neymar arrived in Paris as PSG's star man but he has company at Parc des Princes, where Mbappe continues to shine.
And Neymar's seven-year-old son - Davi Lucca da Silva Santos - is a big admirer of the French teenager and World Cup winner.
"My son loves Mbappe a lot," Neymar said. "I took him to training and he was talking about Kylian all the time.
"He wanted to take a picture to show his friends at school, he took it and was very happy."
Mbappe's quick-fire four-goal haul means no player has scored four goals in a single Ligue 1 match quicker over the last 45 seasons.
The former Monaco forward also became the youngest player – at 19 years and nine months – to score four goals in one game in the same period .
And while Neymar has sometimes been seen as combative with other stars, he says he knows the value that Mbappe brings to the side and that, despite his age, the French star is already a leader on the team.
"I know my value, I know the pressure that exists, I know my responsibilities," the Brazilian said. "But we have many quality players who also have their responsibilities.
"Kylian is one of them. He is a technical leader and the group respects him. As soon as he opens his mouth to say something we listen to him and understand him, no matter how old he is.
"This is a group where everyone knows the importance of each and tonight I want to congratulate him.
"He could have scored even more," Neymar continued with a laugh. "For me it's a phenomenon, a crack, I hope it will continue like that for several years because football will thank him."