When a party is indispensable to a cause, so it cannot proceed without him, the nonjoinder may be raised by plea, demurrer, or may be taken by the court ex mero motu at the hearing. Sawyer v. Baker, 66 Ala. 295; Carwile v. Crump, 165 Ala. 206, 51 So. 744. The present owners of the bonds are unknown to the complainants.