A source tells ET that there is 'no bad blood' between the exes.
"He doesn't have any lingering romantic feelings for Megan or any anger," the source says of Green. "Brian is happy for her, but it really isn't affecting him one way or the other. There's no bad blood or ill will between them at this point."
Green and Fox were married from 2010 to 2021 and share three sons, Noah, 9, Bodhi, 7, and Journey, 5.
The source notes that Green "mainly feels indifferent towards [Fox's engagement] and is just glad they are co-parenting well together."
"Megan really centers MGK and grounds him. MGK's life can be chaotic and all over the place, but Megan brings out a his calmer side," the source says. "She is a really humbling force for MGK, especially when he's on the road or making music."
As for MGK, the source says "he feels like she is the thing that he can go home to at the end of the day and feel at peace with."
"They're both very happy together and can't wait to start their lives together and get married," the source adds.
MGK popped the question with a unique ring, which he explained the meaning of on Instagram.
"I know tradition is one ring, but I designed it with Stephen Webster to be two," he wrote. "The emerald (her birth stone) and the diamond (my birth stone) set on two magnetic bands of thorns that draw together as two halves of the same soul forming the obscure heart that is our love."
In an interview with Vogue shortly thereafter, MGK revealed another feature of the engagement ring. "The bands are actually thorns. So if she tries to take it off, it hurts," he said. "Love is pain!"