But allegations that Affleck had an affair with a family nanny – which the star strongly denies – point to the considerable strain between Affleck, 42, and Garner, 43, as detailed in this week's PEOPLE cover story. Garner was "livid" when she found out, a friend of nanny Christine Ouzounian told PEOPLE. A source close to Affleck has maintained that "there has never been a romantic or sexual relationship" between Affleck and Ouzounian.
The ex-couple have said they plan to work out their plan for dividing their fortune and properties using a private mediator – and that plan hasn't changed, a source close to Affleck confirms. Any alleged bad behavior by either party wouldn't affect mediation, in which parties "try to work out all the different terms to their mutual satisfaction" in a private meeting, explains Sorrell Trope, a veteran L.A. family law attorney who's represented stars including Britney Spears and Hugh Grant.
Even if the stars aren't able to agree on terms and wind up in court, their behavior wouldn't affect who gets what in the divorce. A judge would enforce any prenup, unless it's contested, and otherwise all assets accumulated during the marriage would be divided evenly, with child support awarded as determined by the court.
But child custody is a different situation, in which judges rule based on what's in the children's best interest. A parent's "behavior can affect the terms of custody," says Earle Lilly, a family law specialist who has represented George Foreman and Alex Rodriguez's ex-wife Cynthia. An alleged affair with a nanny could be "significant in a decision of sole custody and joint custody" if Garner were to decide to push for greater custody of Violet, 9, Seraphina, 6, and Samuel, 3, Lilly says. However, Garner "may not want to bring up those things and want to keep it private and quiet."
Any bid for sole custody would depend on the parent's ability to prove it's in the children's best interest, says Trope. "Otherwise you're going to wind up with some form of joint custody."
Trope explains that in California, joint physical custody does not necessarily mean a 50/50 time share. "You could have joint custody with 30/70 or 40/60," he says, noting that an even split is also "very common."
So far, of course, Affleck and Garner have shown they've been able to put their differences aside, spending time together with their kids while Garner films her latest movie, Miracles from Heaven, in Atlanta. "They want to make sure that this is as easy as they can make it on the kids," a source close to the couple told PEOPLE. "They still do love each other and love their children."
Reporting by CHRISTINA DUGAN
For much more on Affleck and Garner's difficult split, the nanny allegations and how Garner is coping, pick up this week's issue of PEOPLE, on newsstands Friday