Megan Fox's comment on Brian Austin Green's Halloween picture on Instagram uncovered a lot of restrained resentment between the estranged couple who split last year. A new report has claimed that the former couple who were together for 15 years and married for a decade are "struggling to get along" for a while, with Green upset about Fox's ongoing romance with Machine Gun Kelly.

After Megan Fox publicly slammed Brian Austin Green for being "so intoxicated with feeding the pervasive narrative that I'm an absent mother," a source close to the actress told People magazine that the two have been at odds for some time.

"They are struggling to get along and have been for a while," the insider said about the former couple who are parents to three sons, Noah Shannon, eight, Bodhi Ransom, six, and Journey River, four.

Meanwhile, a source close to Green revealed that the actor is having a hard time dealing with Fox's new relationship with Machine Gun Kelly and feels the "Transformer" alum moved on "quickly."

"It's a tough situation. As a dad, Brian is great. He is wonderful with the boys. The issue is that he is bitter that Megan moved on so quickly with Machine Gun Kelly," the source said, adding that it has been very hard for the "Terminator" actor.

"His behaviour can be pretty immature when it comes to Megan though. He knows how to get Megan upset. In the past, he was advised to chill out and just focus on doing the right thing for the boys," the insider added.

Pictures of Fox and MGK started circulating in May this year, prompting Green to confirm that he had separated with the actress late last year. In an interview later, Green said "never say never" when asked if he would consider reconciling with his ex-wife.

However, the 47-year-old received strong criticism from Fox after he shared a picture with his youngest son Journey dressed in Halloween costume over the weekend, writing: "Hope you all had a good Halloween!!"

Fox wrote in her detailed comment on the picture: "Why does Journey have to be in this picture? It's not hard to crop them out. Or choose photos that they aren't in."

"I had a great Halloween with them yesterday, and yet notice how absent they are from my social media...You're so intoxicated with feeding the pervasive narrative that I'm an absent mother, and you are the perennial, eternally dedicated dad of the year. You have them half of the time," the 34-year-old added. Shortly after Fox's comment, Green took down the post and later shared the same photo but cropped out their child.

Megan Fox Brian Austin Green
Megan Fox and Brian Austin Green got married in 2010 Jason Merritt/Getty Images