About 5 years ago my brother took out a student loan and my father co signed. My brother past away about 3 years ago. My father is semi retired. He works 30 hrs a week. They are garnishing 25% of his salary. My father just found out he has cancer and has to quit working. His only income will be is retirement check. Are they able to garnish his social security check. He lives in Florida.

For student loans I believe they are allowed to since it is a student loan.
With your dad's circumstances and all maybe they can do something.
I would talk to them about it