Is it a valid joint account if only one account owners signs both names. My step parent was not present upon the opening of the account and my parent signed their names.my parent has now passed and the step parent is claiming ownership of this account that my parent signed her name to.

My parent had multiple accounts with large deposits with his name alone and only a small checking account that her name was on correctly.

The signature is required for FDIC insurance and demonstrates acceptance of the contractual terms. There can be a contract without the signature. WHat you are asking though requires an attorney familiar with your state's laws.

Can you explain how there can be a contract with out a signature?