What are the rules for estate planning in Texas for a person not mentally able to make them on their own?

Please ask the bank to look at the signature card for the checking account.  If it is a "pay on death" or "joint with right of survivorship" account, the money goes to the person named and will not be a part of your brother's estate.  If not, you may be able to withdraw half (if it is a joint account) or you may be a mere convenience signer, signing checks for your brother's convenience, and half -- or all -- of the money is still his and will be part of his estate when he dies. In Texas if someone only leaves a home, two people who will not inherit can sign Affidavits of Heirship before a notary stating that you and your brother are the heirs and the only heirs.  These must be filed in the deed records of the county where the real property is located.  While a court will not enforce an Affidavit of Heirship until it has been of record for five years with no one complaining that it is inaccurate, many title companies will issue title insurance permitting a sale of the property within a shorter period, some within months of the death. In Texas if someone only leaves a home, up to $60,000 in household goods and personal effects and up to $75,000 in other property (such as a bank account), the heirs and two people who will not inherit can sign an Affidavit of Small Estate before a notary and present it to the court.  Some courts will only permit this if the heirs are a spouse and/or minor children so it may not be available to you.  Please check with a local probate lawyer. The third possibility is to file an Application to Determine Heirship and Issue Letters of Independent Administration.  To do this you will need to hire a local probate lawyer.