in the case of a grant executed by two or more authors of a joint work, termination of the grant may be effected by a majority of the authors who executed it; if any of such authors is dead, the termination interest of any such author may be exercised as a unit by the person or persons who, under clause (2) of this subsection, own and are entitled to exercise a total of more than one-half of that author’s interest. (b) the author’s surviving children, and the surviving children of any dead child of the author, own the author’s entire termination interest unless there is a widow or widower, in which case the ownership of one-half of the author’s interest is divided among them.