My sister (F 34) is ruining her husband (M 35), can I contact his family?

My sister (F 34) is a textbook narcissist. She is married to the sweetest man (M 35). They dated for 2 years and married for 6 years.

She is completely destroying him. She’s cheating on him with different men, he knows about them. She asked him if he wanted to meet one of them. He declined. I mean what the hell.

He’s never allowed to speak for himself, when we as a family stand up for him, she packs up and they go home. We are made out as the bad ones. I told him to get a divorce, he says that he’s scared of the unknown out there.

Im afraid that this man won’t make it. He is a shell of his old self. Should I contact his family and ask them to step in? They on-line far away from him and my sister always paints this perfect picture of their relationship to them.

Am I an asshole for wanting to get involved in their business?