AceShowbiz -

While most people are so happy for Jennifer Garner and Josh Duhamel after the two are rumored to be dating, one person may not be ready to say congratulations for the rumored couple. Ben Affleck, Jennifer's ex-husband, reportedly is "getting really jealous" despite him already finding a new love in "Saturday Night Live" producer Lindsay Shookus.

"There were rumors going around about Jen and Josh last year. They did a movie ('Love, Simon') together and there was a lot of talk at the time about them hooking-up," a source reveals to HollywoodLife.com. "Everyone who saw them on set together said they had really obvious chemistry. Jen had filed officially filed [sic] for divorce from Ben and Josh was already separated from Fergie [a.k.a. Stacy Ferguson], so they were well within their rights. That didn't stop Ben from getting really jealous though."

The Batman depicter allegedly "was asking around about it," according to the source. The source goes on saying, "It's fine for Ben to move on and be with whoever he wants, but he's not ready to see Jennifer do the same."

The "Gone Girl" star reportedly is "not at all mentally prepared for Jennifer to be with another guy, especially not someone like Josh Duhamel." The source adds that Ben is feeling "threatened."

Previous report stated that Jennifer and Josh, who split from Fergie in September last year after eight years of marriage, built their romance during breaks from "Love, Simon" filming. "That's the best time for those intimate conversations, the ones you have at the beginning of a relationship to happen," claimed a source. "Away from home and looking for companionship, it's easy to see what happened."

The source noted that the "Transformers: The Last Knight" actor and the "Alias" alum would make a good couple. "Josh is a homebody and craves the simple life. With Jen, he'd get that in spades. She's very sweet and family-oriented," said the source.