Sophie Turner is back on mommy duty just in time for the holidays … it’s her turn to look after her two children as part of her child custody arrangement with Joe Jonas … but a family reunion may be in the cards.

According to new legal docs, obtained by TMZ, Sophie’s got the kids through Jan. 7 … which means she’ll probably be celebrating Christmas and New Year’s with Willa and Delphine over in London.

But, get this … Joe is in England too — he was recently spotted at London hot spot Chiltern Firehouse — so it appears there’s at least a decent chance Joe will get to see the kiddos on Xmas too.

Of course, the big question then becomes … will Sophie and Joe spend time together with their daughters for the holidays, which are traditionally a family affair?

The girls have been with Sophie since Dec. 16 … and they’re allowed to travel with her in the United States and the United Kingdom … but the kids have to be dropped back off to Joe in NYC on Jan. 7.

Remember … Joe had the kids for Halloween and Thanksgiving, so the parents are splitting holiday duties under their temporary child custody agreement as they work through a divorce.

Meanwhile, Sophie was spotted making out with British aristocrat Peregrine Pearson earlier this month in London … before she had the kids.

The best thing about divorce … two Christmases!!!