I have a question. My kids grandfather passed and might have left them money but I don’t get along with his wife or family. What do I do

In short, it depends on how money was left to them.  If your children were beneficiaries under a Will they must be notified if a probate of the Will is started.  You can check the probate court in the county where the grandfather resided when he died to see if a case has been opened.  If they were listed as beneficiaries under something like a life insurance policy, that's when things get tough.  Somebody would have to know about the policy and notify the company that he has passed away.  The company administering the policy would send out a claim form to any beneficiaries.  Best of luck.