My son is 17 he gets disabilty through his dad. He did live with mom. He went to stay with dad 1 month ago. The dad now wants his disabilty to go to him.
I think my son will move back with me. What do I do.

I take it you are the mom? You shouldn't refer to yourself in the 3rd person.

If your son is now living with his dad, the disability should be with the dad. The disability should follow the son.

Of the son moves back with you, then the disability should come back to you.

The disability should follow the son and go to the parent who is current having custody over him.

Should the parent be using the disability check, or should the child? My mother never told my brother about the check and simply banked it away for his future.

The disability check is the son's, for his use and expenses. So where ever he is, so go the check.

Now at 17 you also have the issues of who the legal guardian is, though the courts ( child custody).

Since the guardian or parent who has "legal" custody" which is not always physcial custody, also has rights as to decide where the check goes, or even where the child goes.

You all could fight this out till the child is 18 or just agree and do what is best for the child.