What should the children do when their parents fight and won’t resolve their issues?

I’m in the midst of serious family problem. My father (70 years) and mother (55 years) have been married for 28 years. I’m the eldest son, 27 years with 2 sisters and 1 younger brother. My parterns very often fight with each other since our childhood. All the time abusing each other. This reached it peak when six months ago my father accused my mother of adultery out of anger. My mother was about to commit suicide. My father goes to the houses of all our relatives and tell them false stories of how bad our mother is. My mother is in serious depression. Now my sister is about to be married. But my father still behaves like that. Now my mother asks me and my younger brother to hold our fathers neck and ask him to stop his misdeeds. On the other hand my father always abuses my mother everyday. I know both are at fault but most of the time its my father who has not control on his anger and make a bigg issue out of nothing an starts abusing my mother. They dont want to sit down and and solve the problem. Always the fights are on petty issues. We cannot tolerate this any more. Please tell us what we children, especially the sons do in case the parents behave like this.