Selma Blair is celebrating her son Arthur Saint on his 12th birthday.
The "Legally Blonde" actress, 51, took to Instagram on Tuesday to share a loving tribute to her only child, whom she shares with fashion designer Jason Bleick.
MORE: Selma Blair brings son Arthur as date to premiere of documentary about her MS battle"My Saint, Arthur, happy birthday 🎂," she wrote in the caption alongside a slideshow of photos of her and Arthur throughout the years. "This has been the most incredible life with you. Forever my favorite, I know you are going to have the best year yet."
The "Cruel Intentions" actress continued, "I am so proud of who you are and have become. Usually 🦁. The most adorable little kid has grown into a 12 year old!!!! 🐣🦅. I love you and I like you. Massively. 💛 mom."
Blair was joined by Arthur at at the premiere of her documentary "Introducing, Selma Blair" in 2021. He was also by her side when she had to bow out of "Dancing with the Stars" season 31 due to the toll it was taking on her body.
Blair was diagnosed with multiple sclerosis in August 2018. She has since been open about the condition and wrote about her experience with MS in her book "Mean Baby: A Memoir of Growing Up," which debuted in 2022.