"Basically, every single person who Jen loves attended".
"For well over a decade now they have lived totally separate lives and so not surprisingly, they have become totally different people than who they once were when they were together", said the source.
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The source continued, "Brad, for long, was a very important part of Jen's life".More news: European Union cuts 2019 eurozone economic growth forecast
"They hugged and chatted for a bit, but Jen was busy making sure all of her other guests had an incredible time", the source shares.
On Saturday, the actress' ex-husband, Brad Pitt, was photographed at the Sunset Tower Hotel in Los Angeles, where the celebration was held. However, Pitt was spotted arriving at the party wearing a flat cap, making it hard to make out if it was him.
Other guests included Gwyneth Paltrow (another Pitt ex), John Mayer (another Aniston ex), Katy Perry (Mayer's ex) & Orlando Bloom, Courteney Cox, David Arquette (Courtney's ex), Lisa Kudrow, Barbra Streisand, George & Amal Clooney, Reese Witherspoon, Demi Moore, Laura Dern, Kate Hudson, Keith Richards, Ellen DeGeneres, Robert Downey Jr. and many more.
Earlier in the evening, Jennifer, who turns 50 on Monday, stunned in a strappy black jumpsuit and heels as she entered the historic hotel, which is reportedly her favourite Hollywood hotspot.More news: Francisco Lindor Out 7 To 9 Weeks With Right Calf Strain
Pitt and Aniston were married from 2000 to 2005, and remained amicable over the years, but a source tells People that the pair weren't close by any stretch of the imagination.
Aniston and Pitt started dating in 1998.
However, a source told press in February of previous year: "They aren't in regular contact, beyond an occasional text back and forth to wish each other the best when there's been a new project or big event".More news: Virtual Reality in Education Market Development and Trends Forecasts Report 2018