I recommend that you don't do or say anything, or say very little and then only to your parents. This should primarily remain an issue between your sister, her husband and your parents. You may not like it but it's not your issue. Your parents need to be the ones to decide to stand up or not. They are the ones being put upon, not you.
I remember your brother in law sticking his nose in your parents business from a previous thread. Why should things have changed?
I remember your brother in law sticking his nose in your parents business from a previous thread. Why should things have changed?
Being told you're delusional does not necessarily mean you're mental.