An eyewitness tells ET that Pitt arrived at his ex-wife's birthday party with his security team.
She loves to show off her yoga-honed physique - and she should!
Brad and Jen were once Hollywood's darling couple but ended their marriage in 2005 after five years.
Aniston has been focusing on her work, including her upcoming Apple series, which she is executive-producing alongside Reese Witherspoon. Paltrow posted her own tribute to her good friend Jen as well. As the source reminds us, "Basically, every single person who Jen loves attended".More news: Cardi B Makes History at Grammys
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'Happy Birthday to this fierce Woman, ' he wrote, sharing a black and white image of Jennifer holding a set of bull horns over her head. "Many of his close friends were at the party too". "That included Brad. The party was a celebration of Jen's life". Somewhere out there, we hope the former "Friends" star is sipping some bubbly and toasting her 50 years on this planet.
The "Cake" actress - who split from Justin Theroux last February after two years of marriage - recently insisted she still regards her relationships with both Brad and the "Leftovers" actor as "successful".
After dating for nearly a decade and with six children together, Pitt and Jolie married in 2014, only to file for divorce two years later, after Jolie accused Pitt of heavy drinking and an altercation with their son Maddox, 17. "We are two best friends who have chose to part ways as a couple, but look forward to continuing our cherished friendship", they said when they confirmed their separation.
She said: "I don't feel a void".