Brian Austin Green’s ex-fiancée Vanessa Marcil SIDES with his estranged wife Megan Fox

Brian Austin Green’s ex-fiancée Vanessa Marcil sided with his newly-estranged wife Megan Fox, and detailed the ‘complete devastation’ he put her and their son Kassius through in their ongoing 13-year court battle.

The 51-year-old Daytime Emmy winner Instastoried that she ‘actually has respect’ for the Tennessee-born 34-year-old ‘living her life for herself’ and moving on with co-star Machine Gun Kelly.

Marcil – who boasts 153K Instagram followers – wrote: ‘Megan finally living her life for herself is in itself a gift to her children.’

Megan legally separated from the 47-year-old San Fernando Valley native for the second time in May after nearly a decade of marriage.

Brian – who ended his two-year engagement to Vanessa in 2003 – was spotted Saturday sporting a camouflage neck gaiter and checkered Vans shoes to grab iced coffee to go in Calabasas.

In 2006, Green and his former Beverly Hills, 90210 castmate began their bitter court battle for full custody of their 18-year-old son Kassius leading to him sue her in 2012 over $200K he allegedly ‘lent her.’

After the Cross 3 action star’s ‘frivolous’ case was thrown out, he decided to cruelly cut then 11-year-old Kassius from his life in 2013 and did not see him again for five years.

‘I speak, actually, very kindly about Kass’ father. I just speak the truth now at my son’s request in order to help my son heal and not shoulder these secrets anymore. If his father’ actions reflect poorly on him that is his doing. Not mine,’ Marcil (born Ortiz) replied to a fan.

‘I speak with empathy regarding Kassius’ dad considering the complete devastation that my son went through. My son and my family will tell you the same. I’ve had a rule all through our 13-year court case in my family that “no one is ever to say a bad word about Kass’ dad.”

‘I just finally, now that Kass is grown, tell the truth regarding our court case and him cutting his son out of his life for five years. If you look back at our history, his father publicly tried to slander me, lie about me, shame me as a working mother, and take full custody of my son. I never commented. He admits this now. He’s lucky that I don’t “speak poorly” of him after what he put our innocent boy through.’

Vanessa also made a dig at Brian, writing: ‘He’s very big on doing things that publicly make him look like a nice guy. However, it is who you are when no one is looking that shows your true character.’

Green and Fox will next celebrate the 8th birthday of their son Noah Shannon on September 27, and they’re also parents of six-year-old son Bodhi Ransom and four-year-old son Journey River.

The BH90210 producer-star – who’s recently canoodled with Courtney Stodden and Tina Louise – keeps busy with his podcast and his three-year-old tech venture InteliQore with Jennifer Flynn.