I am so sorry for your loss.  Your Mom died what is called "intestate" meaning without a Will and while you and your brother are not responsible for the bills, her estate is responsible to pay them.  What you have to do is file a Petition in Probate Court to be appointed as the Personal Representative.  Your brother can consent so he does not have to miss work.  When dealing with the hospital try and negotitate the bill.  They will often reduce it.  Good luck.