Do I have any legal obligation to pay any of the bills owed by my brother, who just died of cancer in Jacksonville, FL? What should I do about them?

My brother, who lived in Jacksonville, just died of cancer, leaving behind no will, very little money, and many thousands of dollars in debts. Before he died, he made me a joint account holder on his credit union account, and I used the little amount of money in that account to pay his rent (before he died) and pay for his cremation and death certificate. I have now received in the mail a host of unpaid bills that he had no money to pay since his social security and military retirement payments have been stopped.