No, you cannot sue them. What they do is legal, regardless of your opinon of the product; and when used appropriately (e.g in moderation) is safe. They are not responsible for your brother's misuse of their product or his other issues or behavior.Your brother is the appropriate target for action. If he is not a tenant (not paying rent), you ask him to leave at any time and if he won't, can have the legal system (e.g. a sheriff or court officer) remove him by filing an action "for ejectment" (eviction for nontenants) and getting the court to order his removal. He has no right to remain there is the property owners want him out, so you can remove him if you choose.