My question is, does ownership of what is alleged to have been stolen also need to be proven?

Theft in my country is a criminal case and like all criminal cases it has to be proven beyond reasonable doubt and the burden of proof is on the plaintiff. My question is, does ownership of what is alleged to have been stolen also need to be proven? For example if plaintiff sues defendant for theft of monies from his/her bank account yet evidence shows that bank account does not belong to plaintiff but to plaintiff business partner. Is the fact that the plaintiff does not legally own the account material or what is material is the theft itself irrespective of ownership of bank account?