(a) Except as otherwise provided in Code Section 53-4-49, the marriage of the testator, the birth of a child to the testator, including a posthumous child born within ten months of the testator's death, or the adoption of a child by the testator subsequent to the making of a will in which no provision is made in contemplation of such event shall result in a revocation of the will.

(b) A provision in a will for a class of the testator's children shall be presumed to be made in contemplation of the birth or adoption of additional members of that class, absent an indication of a contrary intent, and the mere identification in the will of children already born or adopted at the time of the execution of the will shall not defeat this presumption.