The former spouses were reunited over the weekend, when Pitt attended Aniston's 50th birthday party at the Sunset Tower in Los Angeles, California.
"Jen arrived alone but was excited to get inside", a source told E!
A source adds, "Jen and Brad have remained friends and have spoken with each other quite a few times since they both became single".
A fusion of yoga, martial arts and animal locomotion, it's the workout that helped Jennifer Aniston overcome her painful split from first husband Brad Pitt in 2005.
"Brad, for long, was a very important part of Jen's life".
A source told People website that Aniston was "very happy that he showed up" and "they hugged and chatted for a bit". "That included Brad", the source continued. "They hugged and chatted for a bit, but Jen was busy making sure all of her other guests had an fantastic time". Mayer's ex, Katy Perry, attended the party too - with boyfriend Orlando Bloom.
Meanwhile, Gwyn posted a similar series of images, captioning it: "Happy birthday (last night and tomorrow) to #jenniferaniston our ray of sunshine, example of perpetual goodness".
"Love these ladies", Hudson wrote.
It is believed she ducked out of her birthday bash at around 1am in the morning.
The great and the good of Hollywood turned out to mark a big occasion for Jennifer Aniston last night. We have these clichés around all of this that need to be reworked and retooled, you know?
She also said at the time that, with Pitt, there was "a sensitivity chip that's missing" after he appeared pre-split in a WMagazine feature with Jolie that showed them as a 1960s married couple.