Richie and Disick have been officially dating since last September after initially sparking romance rumors a year ago. In recent months, the relationship appears to have gotten increasingly serious, with Richie spending plenty of time — and even vacationing — with Disick and Kardashian’s three children: sons Mason, 8, Reign, 3, and daughter Penelope, 5.
“It helps that Kourtney now trusts Sofia,” a source tells PEOPLE. “The kids are allowed to spend time with her. Sofia likes having them and helps Scott. So far, the kids are giving Kourtney good reports about Sofia.”
“Sofia has shown over and over again that she is willing to stay with Scott even when things are not great — but Scott is doing well lately,” continues the source, adding that the father of three “isn’t really partying” and “spends a lot of time with his kids.”
Richie, 19, and Disick, who just turned 35, are currently celebrating his birthday in St. Barts with his kids.
Documenting his birthday dinner on Saturday, the proud papa shared a sweet photograph of himself kissing his youngest son Reign.
Richie wished her man a happy birthday with a photo of the two getting cozy in the water. Later that evening, she shared a photo on her Instagram story of the couple sharing a kiss on the lips.
“Happy birthday babe! Thank you for being you,” she captioned the post. “Love you.”
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RELATED VIDEO: Sofia Richie and Scott Disick Kick Off Their Christmas Weekend Together
While a source previously told PEOPLE that Kardashian, 39, still thinks Richie is “too young” for Disick, the couple has her blessing so long as their relationship helps keep him on track.
“Sofia is helping Scott be a better, healthier person,” said the source. “Kourtney feels confident that Scott and Sofia takes good care of the kids. Scott is a great dad when he has his life together.”