Kelly Osbourne is smitten.
The Fashion Police alum, 37, posted a handful of photos on her Instagram Story earlier this week wishing Slipknot's Sid Wilson a happy 45th birthday — but a source tells PEOPLE that the musician's appearance on her social media shouldn't come as a shock, considering they've known each other for more than 20 years.
"Kelly and Sid met when his band was touring with Ozzfest in 1999," says the source, referring to the music festival founded by her parents, Sharon and Ozzy. "They have remained friends since. They are very happy together."
While Osbourne and Wilson have yet to make an official appearance on each other's Instagram grids, the former reality star posted a series of photos last Saturday showcasing custom pillows of herself and Wilson, which were made by friend Oleg Lee, who goes by the moniker That Pillow Guy on social media.
"Thank you @thatpillowguy (not to be mistaken for that other guy) for our amazing pillows. We are #obsessed!!!! There are so many things I want to turn into pillow. I will be hounding you! Sorry in advance 😂," Osbourne captioned the carousel of pics, one of which featured the same pillow that Wilson posted on his Instagram.
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
Although Osbourne had never confirmed her previous relationship before being seen with Wilson — she had been spotted with filmmaker Erik Bragg on numerous occasions in 2021 — she credited an unnamed boyfriend for helping her when she relapsed in April last year after nearly four years of sobriety.
"I only want to be the best version of myself, for my family and my boyfriend and my friends and I was not. I was the furthest thing away from that," the TV personality said during an appearance on Facebook Watch's Red Table Talk in June last year.
RELATED VIDEO: Kelly Osbourne Reveals She 'Relapsed' After Almost 4 Years of Sobriety: 'Not Proud of It'
Osbourne's recent appearance with Wilson comes shortly after her brother, Jack, proposed to his partner of more than two years, Aree Gearhart, ahead of New Year's Eve.
"Today I asked the most beautiful and loving woman I've ever met to marry me. She said yes!!" Jack captioned a selfie of himself and his fiancée, who flaunted her gorgeous ring while they posed outside in their snow-covered surroundings.