They all looked so comfortable together. On a mid-December stroll in LA with Anna Faris, cinematographer Michael Barrett casually carried Jack — her 5-year-old son with estranged husband Chris Pratt — atop his shoulders. Just a few days later, Jack and Michael were photographed bonding again, this time at California’s Redondo Beach Pier, where they enjoyed fish and chips with Anna and his son from a previous relationship. “Anna,” says an insider, “is already blending their families.”

Chris was heartbroken to see the photos of his son with the other man. While the pair quietly split in July, the Guardians of the Galaxy star didn’t file legal documents to end their eight-year marriage until Dec. 1 — and now “the divorce is getting ugly,” the insider tells In Touch exclusively. “Chris is having major problems with Anna’s new boyfriend co-parenting their son. They’ve been arguing about it.” Chris, 38, doesn’t necessarily mind that Anna, 41, began flaunting her romance with Michael, 47, in September, just a month after they publicly announced their separation, adds the insider, “but giving Michael ‘daddy duties’ is pushing it. Chris feels she’s gone too far.”

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Anna and her new boyfriend, Michael, spotted in Venice, Italy on Nov. 15, 2017.

Anna doesn’t seem to care. “She’s happy with Michael — she’s always with him and wants the whole world to know about it. But Chris says it’s not fair to Jack, having to meet a potential stepfather figure so soon after his parents’ breakup,” explains the insider. Anna and Michael are moving so fast, they were spotted house-hunting together in LA’s Venice neighborhood in early December. “No dad wants his young son cared for by another man so quickly.”

At the very least, Chris feels Anna should have discussed her intentions with him. “She didn’t sit Chris down and say, ‘Jack is going to meet Michael.’ That conversation should have happened first, but it didn’t. That’s why Chris was so upset,” says the insider. “The conversation happened after the photos of Jack and Michael came out.” If Anna told Chris that she and Michael were engaged, explains the insider, “then that would be a different story. But until then, she needs to create some better boundaries.”

Anna would love Michael to become husband No. 3 — and Jack’s stepdad officially. “She plans on marrying him. And Michael wants to marry her, but he’d like to propose once the divorce is finalized,” says the insider. “Does Anna think she moved too fast? Yes, but that’s just how she does things.” In her 2017 book, the Mom star admitted she hooked up with Chris immediately after leaving her first husband, actor Ben Indra, in 2007. “There’s no grace period in Anna’s world,” explains the insider.

But the divorce could drag on if Chris and Anna can’t make peace. “They have 50/50 custody for now,” says the insider, “but the fights have gotten heated. And it could get worse.”