You have to involve your wife in this matter. There might be a possibility that they are doing it unintentionally. It would be better if you don’t talk to them directly about this matter. You and your wife can discuss this matter first and then can take steps accordingly. Ask her to confront your in-laws about this. They might get understand and won’t do that again. Or you have to learn to say no to your in-laws. If they will ask for money, you can simply deny to give them money. After this, they won’t be able to financially exhaust you out.