Younger brother Roberto burst into tears after scoring his first goal in Serie A to put Benevento into the lead in the first half.
At half-time, he told DAZN: "I'm very, very happy but I'm sorry to have scored my first Serie A goal against my brother!”
Napoli captain Lorenzo ensured there would be no hard feelings by hitting an excellent goal in off the crossbar midway through the second half to level the scores. Andrea Petagna scored the winner for Napoli soon after.
It was only the second time in Serie A history that two brothers have scored against each other in a game. Hungarian pair Istvan and Ferenc Nyers did the same back in 1949, while playing for Inter and Lazio respectively.
While Roberto was delighted to get his first goal in the top flight, Lorenzo is closing in on 100 goals for Napoli, and now has 92 in all competitions.
Both were born in Naples. Roberto began his career at Napoli, making his debut in the Europa League in 2012, but he hardly featured for his hometown club and was sent out on loan on six occasions.
He represented Perugia, Reggina, Avellino, Latino and Parma before first joining Benevento on loan as they finished bottom of Serie A in 2018-19. He made the move permanent the following summer and helped them to the Serie B title last season.
The Insigne brothers are far from the only pair of siblings to feature together in Serie A.
The pairs of Franco and Guiseppe Baresi, plus Fabio and Paolo Cannavaro both made more than 800 appearances in the competition between the two.
Filippo and Simone Inzaghi, Cristiano and Alessandro Lucarelli and Sebastien and Nicolas Frey are among the other well-known pairs of brothers to have played in the Italian top flight.
In the 1940s and 1950s, five Sentimenti brothers – Lucidio, Vittorio, Primo, Ennio and Arnaldo – were all regular fixtures in Serie A, the former pair often playing together for Juventus.