More details are coming to light on the timeline of Joe Jonas and Sophie Turner's swift split.

In fact, the Game of Thrones actress said that the "breakdown of the parties' marriage happened very suddenly" in a lawsuit she filed against her husband Sept. 21 and obtained by E! News. 

Per her filing, the couple planned for their daughters—3-year-old Willa and a 14-month-old whose initials are DMJ—to go on tour with the Jonas Brothers singer in August while Sophie was filming the TV series Joan in England. 

Sophie was able to travel back stateside attend the Jonas Brothers' Aug. 13 concert at Yankee Stadium, where she was pictured cheering him on in the New York crowd. The next day, the 27-year-old posted a photo of herself kissing Joe's hand backstage, writing on Instagram, "long long New York nights."

However, Sophie said in her lawsuit that she and Joe "had an argument" just one day after her post—on Aug. 15, which was his 34th birthday. The same day, the HBO star celebrated his milestone by sharing a pic of them in matching pajamas and writing on her Instagram Story, "Happy birthday handsome." 

For his part, Joe rang in his birthday with his family and friends—but Sophie wasn't pictured in any of the party photos he posted Aug. 15 with the caption, "I am very lucky." His mom and dad Denise and Kevin Jonas; brother Nick Jonas and sister-in-law Priyanka Chopra; and friends including NFL star Aaron Rodgers were all pictured.

It was about two weeks later that his breakup with Sophie was made official.

"On or about September 1, 2023, the Father filed a divorce case against the Mother in Florida," Sophie's petition states. "On or about September 5, 2023, the Mother found out through the media that the Father had filed for divorce."

She said the pair "agreed" prior to the breakup that she would pick up their girls in the U.S. and take them back to England on Sept. 20, but she alleges Joe now "refuses" to hand over their daughter's passports so that their kids could travel home.

In response to her legal petition, Joe's rep told E! News Sept. 21 that Sophie was aware he was going to file for divorce and denied that he "abducted" their kids.

"This is an unfortunate legal disagreement about a marriage that is sadly ending. When language like 'abduction' is used, it is misleading at best, and a serious abuse of the legal system at worst," the rep said in a statement. "After being in Joe's care for the past three months at the agreement of both parties, the children are currently with their mother. Sophie is making this claim only to move the divorce proceedings to the UK and to remove the children from the U.S. permanently."

The "Sucker" singer's rep said the pair met up to "work together towards an amicable co-parenting setup" before Sophie's filing.

Furthermore, the Disney Channel alum's rep stated, "Joe is seeking shared parenting with the kids so that they are raised by both their mother and father, and is of course also okay with the kids being raised both in the U.S. and the UK."

E! News reached out to Sophie's rep in response but hasn't heard back.

Scroll on to see more of Sophie and Joe's outings together.