Legal or intestate succession takes place:
(1) If a person dies without a will, or with a void will, or one which has subsequently lost its validity;
(2) When the will does not institute an heir to, or dispose of all the property belonging to the testator. In such case, legal succession shall take place only with respect to the property of which the testator has not disposed;
(3) If the suspensive condition attached to the institution of heir does not happen or is not fulfilled, or if the heir dies before the testator, or repudiates the inheritance, there being no substitution, and no right of accretion takes place;
(4) When the heir instituted is incapable of succeeding, except in cases provided in this Code. (912a)