Brian Austin Green has told Machine Gun Kelly to "grow up"

Brian told TMZ: "I didn't even know."

The 51-year-old actor - who also has Kassius, 22, with Vanessa Marcil, and Zane, two, with fiancee Sharna Burgess - then audibly sighed when told about what Megan allegedly found on MGK's phone.

He added: "How old is he? ... He's in his 30s, isn't he? ... But in your 30s, like, f***. Grow up. Like, she's pregnant.

Brian wants nothing but the "best" for Megan, who he was married to from 2010 to 2021.

He said: "I just want the best for her. I want the best for the baby. I want the best for our kids. That's a shame."

"I'm heartbroken about it because I know she's been so excited.

"And the kids are so excited for life and the change and all of that."

Brian stressed he doesn't know "the facts" about the couple's split, but still thinks the news is "tragic".

It was previously claimed the 38-year-old beauty is "done" with MGK for good.

A source told DailyMail.com: "Megan was just done with all of it. She was done with his behaviour and the way that he treated her.

"When she fell pregnant, he thought it meant that she would stay with him no matter what - and it is not the case.

"The most important thing in Megan's world right now is her unborn baby and she has no problem raising the child on her own.

"She's left him before, but this time seems final."

Another insider told the publication the pair's relationship has always been up and down but it hit a low point over Thanksgiving weekend.

They explained: "The way they operate is drama. It's like a never-ending high school relationship. For weeks and months, everything was fine but when they get into fights, it is all or nothing. It took a turn for the worst during Thanksgiving."