"Plus, he's not intimidated by Kylie's empire," the insider said, adding that while fans were surprised by the couple, those close to the beauty guru think they make perfect sense together.
"They're both so busy with work that when they come together, it's just a good time," the source explained. They also noted Chalamet understands Jenner's children, Stormi, 5, and Aire, 16 months are her main priority.
"He would never want to get in the way. He's sensitive and kind," the insider shared.
The two celebs have allegedly spent most of their time at the Little Women alum's Beverly Hills home.
"They like to sit outside drinking a glass of wine together," they spilled. "Timothée is a calming influence on Kylie, and she's super impressed by his work. He's one of the youngest Best Actor Oscar nominees ever!"
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"Both of their relationships are thriving," the source said. "Kylie and Kendall are extremely happy."
As OK! previously reported, while Kylie and Timothée have yet to confirm their relationship, paparazzi caught them hanging out with their siblings at the 27-year-old's house.
The couple was seen enjoying a barbecue in the backyard along with Kendall and Pauline Chalamet.
The Kylie Cosmetics founder wore leggings, a black leather jacket and riding boots, while her older sister stepped out in a black T-shirt. Pauline had on a blue and tan flannel with black shorts and a white shirt.
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Additionally, The Kardashians star had an outfit change as other images captured showed both Timothée and Kylie in matching tie dye T-shirts.
The family time came after a source claimed the two hang out almost every day, saying they are together "for upwards of six days a week." Meanwhile, another insider alleged the pair is "not serious."