On Friday, Jenner, 22, shared an Instagram montage video of her birthday extravaganza in Capri, Italy. In the video, Richie, who is dating Kourtney Kardashian‘s ex Scott Disick, called Jenner her “best friend” in a sweet message.
“Kylie, you’re 22 and you’ve always been one year cooler than me,” said Richie, 21. “But I love you. You’re my best friend. I don’t know what life would be like without you.”
Richie echoed her kind words about Jenner in the comments section of the video, writing, “Love you so much!”
The Keeping Up with the Kardashians star’s boyfriend, Travis Scott, and their daughter, Stormi, also appear in clips from the trip, as does family matriarch Kris Jenner, who tells her youngest daughter, “I’m so amazingly blessed to have you as my daughter and to have you call me mommy.”
Jenner and Richie have grown closer due to Richie’s relationship with Disick, 36. (Disick shares three children — Reign Aston, 4½, Penelope Scotland, 7, and Mason Dash, 9½ — with Kourtney, 40.)
At Jenner’s birthday bash in Capri, the couple, who have been dating since 2017, was seen walking arm-in-arm, with Richie wearing a coral-colored dress and Disick matching her in a salmon-colored jacket.
The model shared a slew of Instagram photos from her European travels celebrating Jenner’s birthday this month, including a snap of herself wearing a tiny black bikini on a yacht.
Last weekend, Richie, Disick and Jenner hung out again, this time to celebrate Richie’s 21st birthday in Las Vegas, where they were joined by Jenner’s pal Anastasia Karanikolaou.
Richie, who was dressed in a pink, crystal-embellished Yousef Al-Jasmi catsuit, hit up XS Nightclub, where The Chainsmokers were headlining that night. Jenner, who wore a pink latex dress, arrived later and was spotted dancing with the rest of the group.
A source recently told PEOPLE that Jenner grew close with Richie after cutting ties with longtime best friend Woods, who kissed Tristan Thompson, the father of Khloé Kardashian‘s 16-month-old daughter True, in February.
“Sofia has been nothing but supportive about the Jordyn drama,” the source said. “She seems like a very loyal friend to Kylie and Kylie appreciates that.”