Why does your brother’s father-in-law want you in on a settlement which you have no power to effect. He probably wants to create your name in a CAW cell complaint or DVA case that they are preparing to file. Stay away. Don’t give them the opportunity. As it is you don’t get along with your brother, so you can not influence him in a settlement. You can file a complaint of harassment and threat against the girl’s father. This will help you in a situation where you are named in any complaint that they decide to make.