My brother and I are selling my recently dad's house who has died.my sister in law keeps interfering in front of prospective buyers. Saying I would knock the price down. It's not her house to sell. Really annoying me.
If the sister in law is your brother's wife then it's better for him to speak to her about it. If he doesn't want to then I'm not sure what you can do. You could say something but might upset your brother.