A source tells ET that the former couple isn't planning on celebrating together.
A source tells ET that Jon and Kate are "still at odds," nearly 10 years after their 2009 divorce. "They will never agree about how to raise the children," the source explains, adding that the two "absolutely despise one another and can't stand to even be in the same room."
The former couple won't be celebrating Collin, Hannah, Joel, Alexis, Leah and Aaden's birthday together, but they do both plan on commemorating the big day.
ET's source says the pair had a close call while shopping at the same party store on Thursday, but Jon exited before running into Kate, who is planning a party for the kids. "Jon is low-key and just wants his kids to be happy on their birthday," the source adds.
Jon took to Instagram on Thursday to share a pic of himself having breakfast with Hannah, before wishing the rest of the brood a happy birthday with a sweet throwback pic. Kate, meanwhile, has been sharing her disbelief over the sextuplets' growing up on Instagram over the past few days.
Jon and Kate's relationship drama has played out over the past few years, with police even being called to an orthodontist's office last August as the former couple argued over custody of one of their younger daughters.
See more on the incident in the video below.
Reporting by Adriane Schwartz.