What do you think about me telling my in-laws to stop buying my kids' clothes?
What would you make them stop buying your kids clothes?
If they really want to help my kids they can look after them and teach them.
I resent my in-laws sometimes too, but you should not get angry about a good thing that they are doing just because you expect him to do something more. Your in-laws buying your kids clothes is it's very noble and something that they did not need to do and you should be appreciative of it. Have you let your kids visit them sometime in the future, so that you can get to know your in-laws better.
You're right and I will buy my kids more clothes.
It's good that you can look at the situation differently. Letting your in-laws know that you appreciate what they do will encourage them to do more.