Son's Wife Is Not Include In the lineal descendant
But , As Per Section 56
Relative Means;-----
(i) spouse of the individual,
(ii) brother or sister of the individual,
(iii) brother or sister of the spouse of the individual,
(iv) brother or sister of either of the parents of the individual,
(v) any lineal ascendant or descendant of the individual,
(vi) any lineal ascendant or descendant of the spouse of the individual, and
(vii) spouse of a person referred to in items (2) to (6) mentioned above.
Since The 7th Clause include Spouse Of Clause 5th
So Son's Wife Is covered U/s 56 , And the Gift to Son's Wife is Not Chargeble To Tax