It’s really tough! I think your husband has major role to play in this situation. Does he accept that his brother and bhabhi are unfair to both of you? If he does, then ask him about solution. This will give you an opening for discussion; do not suggest any solution from your side. Let him think about the solution, you just keep discussion on. Secondly, separate yourself from the joint business may be temporarily or forever; so that they will realize their real worth. It might be too harsh your brother in law but you know some times in life you need to take certain tough decision to make your emotional health better.