The 14-year-old Stranger Things star and her 15-year-old musician boyfriend announced the sad news on their respective Instagram Stories Tuesday.
"The decision with Jacob and I was completely mutual. We are both happy and remaining friends," Brown wrote in her post, which Sartorius echoed in his near-identical statement.
The former couple made it official in January with social media posts. Since then, they haven't been shy about sharing their relationship. On Brown's birthday in February, Sartorius called her the "funniest, most caring person" in a sweet tweet.
Happy birthday to this beautiful girl, 14!! you’re the funniest, most caring person in the entire world. I hope this year brings you lots of great memories and moments you remember forever. Can’t wait to see you, I love you and miss you so much!! ❤️ @milliebbrown pic.twitter.com/x9ttHDNUY2