Two friends have a joint account in a commercial bank. On the death of either one of them who owns the money?

I have a feeling that there are a lot of facts relevant to this matter which are not contained in your email, but let me take a shot at it based on what I know.  Your should be aware, however, that there are factors which can complicate matters which you do not address. For example, did your friend leave any unpaid debts or people with claims against him? Did he leave any surviving spouse who may exercise a right of election? Not sure what you mean about the niece being the second codicil, unless you mean that in a second codicil to the will, all the money was left to the niece.  That may or may not matter, as set forth below. Certain assets pass on according to a person's will, but other assets pass outside the will.  For example, my will may leave all my assets to my girlfriend, but if I own a house as a joint tenant with right of survivorship (not a tenant in common) with my brother, the house passes to him upon my death.  If I have a life insurance policy, the money passes to the beneficiary upon my death, regardless of what my will says. It appears that your friends owned the bank account as joint tenants with right of survivorship.  If your friend agreed with his friend that the bank account would pass to the survivor, that supercedes any will.  If the bank was party to that contract, they should have not have transferred the money to the decedent's niece.  If the bank did not know about the arrangement, however, they may have transferred the money to the sister AS THE EXECUTOR, not in her individual capacity.  Your friend can still recover it, but he will have to make a claim against the estate.