ANSWER:

Either you have evidence that are strong enough to stand in a court of law or you are accusing him based on speculations and suspicion! 

If you have such evidence, either speak to your sister or if he is your husband’s brother, speak to your husband and demand your money from him.

If you don’t have such evidence, you must fear Allah as accusing people on speculations and doubts is sinful!

I lost my money in big amount i know who took it but i cant ask for it because he is my brotherin law. Thats his bad behavior taking people s money . How to make duaa for it .how to make him feel sorry and return my money back . I really in hard situation. Dont know what to do . He is a thief.