The 'gift' is not income if it is received from a 'relative'.
For this purpose, 'Relative' is defined as under:
(e) "relative" means,—
(i) in case of an individual—
(A) spouse of the individual;
(B) brother or sister of the individual;
(C) brother or sister of the spouse of the individual;
(D) brother or sister of either of the parents of the individual;
(E) any lineal ascendant or descendant of the individual;
(F) any lineal ascendant or descendant of the spouse of the individual;
(G) spouse of the person referred to in items (B) to (F); and
(ii) in case of a Hindu undivided family, any member thereof;]
As the donor in your case is the spouse of your lineal descendant, the 'gift' is not taxable as income in your hands.