Sofia Richie and Kylie Jenner's best friendship is going strong.
Shortly after declaring the billionaire makeup entrepreneur and reality star her "best friend," Sofia Richie celebrated the end of her 21st birthday celebration in Las Vegas by sharing a photo of the two, along with a few other gal pals, posing in front of a private jet.
"Best 21st a girl could ask for! Prepare for some serious spam," she wrote.
Earlier in the day, Kylie posted a "throwback" video from her own 22nd birthday extravaganza, which featured messages from her friends and family, including Richie.
"Kylie you're 22, and you've always been one year cooler than me," she said. "But I love you, you're my best friend. I don't know what life would be like without you."
Sofia's ties to the Kardashian clan run pretty deep. In addition to being Kylie's BFF, there's a chance she could potentially be the stepmother of Kylie's niece and nephews, as she has been dating her sister, Kourtney Kardashian's ex Scott Disick — who recently gifted her an Aston Martin for her birthday — for over two years.
While Sofia and Kylie have known each other for years, they reportedly have grown closer in recent months. First, because the whole Scott and Kourtney drama has died down, and second, since Kylie's best friend spot recently opened up, due to the Jordyn Woods/Khloe Kardashian cheating scandal.
"Kylie and Sofia have always run in the same circle and are very close in age, so they've bonded a lot through the years. They've always been in the limelight, lived very similar lifestyles and grown up around a lot of the same people," a source recently told US. "They've gotten a lot closer as of late now that the Kourtney, Scott and Sofia drama has died down. Once any drama between Kourtney and Sofia blew over, Kylie felt more comfortable spending girl time with Sofia again."