Sophie Turner and Joe Jonas's custody battle is complicated due to their globe-trotting lifestyle, a family lawyer explains

Sophie Turner and Joe Jonas's custody battle is not only bitter but messy due to their globe-trotting lifestyle, a legal expert says.

The Game of Thrones actress filed a petition Thursday for the return of their children to England. She accused the Jonas Brothers singer, who she's divorcing, of the "wrongful retention" of their daughters, according to the filing obtained by Yahoo Entertainment. Turner, 27, claims Jonas, 34, won't turn over the American-born children's passports and let her return with them to England, where she claims they moved full-time in April.

Turner currently has the children in New York City, where she filed her federal case, citing the child abduction clauses of the Hague Convention, an international treaty adopted by more than 100 countries, including the U.S. and the U.K., which aims to compel the return of a child taken by their parent from their country of "habitual residence." Jonas filed for divorce earlier this month in Miami, Fla. where they owned a home until last month. His statement said he wants to share custody, even if her home base is England, but filed their divorce case in Miami Dade County — and he feels it's the appropriate jurisdiction for the case.

How is a child's residency determined?

A child's legal residence is determined by where they've resided for the last six months.

"When a child is living somewhere for six months, that place is deemed their 'home state,'" family and matrimonial law attorney Nancy Chemtob tells us.

"So, for example, if you live in Massachusetts for seven months and all of a sudden one spouse says, 'I want to get divorced. I want to take the kids to Colorado,'" she continues. "You can't because it's a six-month rule."

That said, a judge will also take into consideration the best interest of the children.

"That's pretty much standard language in divorce world: Is it in the best interest of the child to, you know, take anti-anxiety medication? Is it in the best interest of the child to take swimming lessons?" says Chemtob, who represented Mary-Kate Olsen in her 2021 divorce settlement. "Whatever is in the best interest of the child [also comes into play]."

This is where things get murky. Jonas claims Florida is home, Turner says Warwickshire, England is home — and yet they haven't lived in either place for six months.

Turner claims England was to be their "forever home."

In the petition, Turner writes that she and Jonas never planned to make Miami their permanent home. In December, while in Warwickshire County, England, for the holidays, they "began to search for their 'forever home'" there to buy for their family. They "left Miami" on March 10, putting their home — the only one they own together — on the market and shipping "many of the children’s personal belongings to England." She claims they officially moved to England on April 10. For the first month, they stayed in a London rental and then on May 5, they moved to a Warwickshire rental.

The children became "fully involved and integrated in all aspects of daily and cultural life in England" immediately, Turner claims. Willa goes to nursery school there. Their dentist and doctor are there. They engage "in extracurricular activities, playdates and cultural activities" there with Willa even taking theater workshops.

Turner says the family was in Warwickshire from May 5 to July 31 at which time Jonas left for his U.S. tour. She explains that she started working on Joan, in production from May to September, so they decided the kids would travel with Jonas and a nanny in the U.S. because his work schedule gave him more time with the kids than hers. When she wrapped on Sept. 14, the plan was she'd fly to New York and get the kids and take them back to England while he kept touring.

In between, Turner says they signed a contract, on July 7, to purchase a home in Little Stoke, Wallingford, Oxford with plans to complete the sale on Dec. 2, 2023. However, they had a fight in New York on Aug. 15 and Jonas filed for divorce on Sept. 5, which she says she found out about in the media. On Sunday, they met to discuss their separation, during which time she claims Jonas refused to turn over the kids passports for planned Sept. 20 travel to England, resulting in her filing her international custody dispute case in the U.S. as well as in the U.K.

File this case under "it's complicated."

The big wrinkle here is that the home state isn't cut and dry. Turner and Jonas have lived all over the place for the last year, according to a list she provided in the filing.

While Miami may have legally been their home until this year, they only spent approximately 11 weeks there in the last year. They were in Warwickshire for 12 weeks, between May and July, but then the kids have been in the U.S. since. They haven't been in one location for six months consecutively.

"This is a tough one because they were bouncing around," Chemtob says, pointing to the list of every location they've stayed for the last year. "When you look at the timeline here, it's so spotty. They weren't in one place."

Turner does try to lay the groundwork for why England is home, talking about the children having routines there as well as medical care, dental care, extracurriculars and playdates.

While Chemtob says Turner trying to claim they wanted to make England a 'forever home' is "irrelevant. If they talked about moving to England, if they talked about splitting their time — you can talk about anything, it's the actions." But they did spend time there, more than they did in Miami, so that could be her argument.

"I would make that case if she were my client," says Chemtob. But she doesn't think it will get that far. "My prediction is they're going to have to settle somehow. I just think that if she really wants to move to England and he wants to stay in the U.S., then they could figure out a custody schedule."

That's Jonas's hope. In a lengthy statement provided to TMZ on Thursday, his rep wrote, "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 children were not abducted. 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 U.K. and to remove the children from the U.S. permanently."

Jonas's statement suggested that he wants to work together with Turner, but she's not cooperating.

"Joe is seeking shared parenting with the kids so that they are raised by both their mother and father, and is of course also OK with the kids being raised both in the U.S. and the U.K.," it noted. "The children were born in the U.S. and have spent the vast majority of their lives in the U.S. They are American citizens."