Ran business w/father for years but business no longer exists, have capital one he signed for w/personal guarantee. He's 76 and doesn't care what I do. I am not listed as a user of card (I have though we have same name, Jr & Sr) If I stop paying them and he is no longer in this state NY ,retired to FL can they do anything to him, he owns home with mortgage on rented lot in retirement community and is on social security. Can they bother my mom? She isn't listed on business or anything.

If he has other money saved, they can freeze his bank accounts and get their money.

Since this is a personal guarantee They can go after his assets, though his home is safe under FL homestead laws.

However, if you have been paying the bill from your personal accounts, they might argue that you assumed responsibility for the debt.