How the hell do you combat parental alienation?

I made a post a few months ago about how my narc grandma was supporting my aunt’s abusive ex-husband over my aunt (her own daughter) in their custody battle. I haven’t made an update to that yet because not much has changed as the May court date just upheld the current temporary agreement and they have another court date set for August and that’s when my statement against my grandma will be read out.

However, in the meantime, my mother has gone to the UK (we live in Australia) to support her sister and I will be going over in August. My aunt’s ex-husband is also a narcissist and incredibly abusive. Despite having a restraining order against him (I think it’s called a non-molestation order in the UK?), he has received zero consequences for breaching it, despite being repeatedly reported to the police.

He torments her and anyone close to her and weaponises and manipulates their kids against her. He lets them do whatever they want and buys them whatever they want so that he’s the “fun” parent, and also coaches them into accusing my aunt and now my mother of abusing them. If my aunt or my mother try to parent them they immediately tell them how much they hate them and how they’re going to tell people they abuse them and that they’ll go to jail. My aunt has documented everything and the court/social services are aware, but in the meantime, how the hell do you combat this???

As I mentioned, I’m going over in August and I know there’s likely very little I can do, but I’m hoping that even though I’m an adult, my cousins might hopefully see me more as a peer than a parental figure and that I can hopefully be a good influence, especially since we have some shared common interests. At the same time though, I have to be prepared for their father to poison their minds against me as well. Does anyone have any advice on how to approach this?