Your brother might not believe you as his wife must have played her part in creating your bad image in his mind. But, do not stop proving yourself right and her wrong. I can suggest some ideas, here we go
You can fit CCTV cameras inside your home. You must talk about this to your parents and even your brother, and make them believe that you have not done anything like this. Find out the reason behind her lie and sort out things accordingly. And, still, if you get no help from the family then you should go for police support and ask them to investigate and prove you right. This way you can keep yourself protected.