Madonna's daughter Lourdes Leon and Homeland actor Timothee Chalamet have reportedly been dating since April this year. Credit: Elder Ordonez/

Madonna is redefining what it means to be a "cool mom." The legendary pop singer, 54, spent the majority of her time at a June 18 after party for the Cinema Society screening of her EPIX documentary Madonna: The MDNA Tour partying with her kids -- and both Lourdes and Rocco looked like they were having a blast.

According to an onlooker, the Material Girl didn't seem to bat an eye when Leon, 16, made out with her boyfriend, Homeland actor Timothee Chalamet

Leon and Chalamet were first linked in April after they were photographed walking side-by-side to a dinner date in NYC on Sunday, April 14. The young couple was accompanied by Leon's father -- and Madonna's ex, personal trainer Carlos Leon -- as well as his current girlfriend.

A source told Us Weekly at the time that the pair were dating, but added that it was in a "loose" sense. "They are teenagers being teenagers so I guess you can call it that," the source said.

At Tuesday's after party, Leon looked like she just wanted to have fun, hanging out with two male friends and later dancing with a group of her pals (mom Madonna later joined in around 1:30 in the morning).

Madonna's son Rocco, meanwhile, had a few break dancers in his group of friends, and was busy partying on the dance floor.

"He's a Leo, what can I say?" Madonna told Us earlier in the evening. "He's disconcertingly comfortable on stage and I was thrilled to see him every night. He gave me a little boost of energy." (Rocco's dad is the pop superstar's second ex-husband Guy Ritchie.)

"Go Rocco, wherever you are!" she continued. "However, he does not look like that [like how appears in the concert film]. In one year, he has grown. He's six feet tall. His voice has deepened and I'm a bit scared of him."

The threesome continued to hold court throughout the event but later left the festivities around 2 in the morning.