Your brother has an estate if he has a mortgage. You need to petition the probate court in your brother's jurisdiction to be appointed the Administrator of his estate. The court will issue Letters of Administration that will enable you to carry on the business of disposing of his estate.
If your brother is the sole owner and there is no outstanding mortgage then he has the right to transfer the property to you by a quitclaim deed. However, if there is an outstanding mortgage the lender can demand payment in full if the property is transferred. If the transfer is done to avoid creditors then the court can invalidate the deed.You should consult with an attorney who can check the title for any outstanding claims and encumbrances and then draft a deed that is proper for that jurisdiction.
Only if he is the executor of the estate and has court authorization.
The creditors will just have to write off the debt. You are under NO obligation to pay his bills. They will try to get you to do it, but you don't have to take it on.
Your children are the first cousins of your brother's children, and the first cousins once removed of your brother's grandchildren.
Your sister's husband is your brother-in-law. Your brother-in-law's brother is not related to you and neither are his children. But he is your sister's brother-in-law and his children are your sister's nieces and nephews.
Assuming the brother who died with a will was unmarried and had no children, and assuming his beneficiary brother predeceased him, his estate would pass to the children of his siblings. If he had only one brother then his brother's children would inherit his estate.
If your brother (or your sister) has children they are your nephews (males) and nieces (females).
Your brother's children would be your nieces and nephews.
Your brother-in-law's children are your nephews and nieces.
An Uncle
Your brother's children would be your nieces and nephews. Your nephew's children would be great-nieces and great-nephews.
Chances are that you mother owned the property, borrowed against it and then deeded it to your brother. Your brother took title subject to the mortage. The best thing to do is to encourage your brother to refinance and get a loan in his name. The existing loan might have a clause that accelerates payment in case of the death of the borrower. It is unclear if the lender would be willing ot continue accepting the payments, but your brother will lose the house in foreclosure if he doesn't make the payments.A Different PerspectiveYou stated that your mother owned the mortgage. That sounds like your brother purchased a home and your mother loaned him the money. That means your brother owes a debt to her estate. If she had a will her property, including the mortgage, will pass according to the provisions in the will. If she died intestate, without a will, her property, including the mortgage, will pass to her heirs at law according to the state laws of intestacy. Your brother owes the balance of the mortgage to his mother's heirs and that may include himself. You can check the laws of intestacy for your state at the related question link provided below. You can add more details on the discussion page.