The natural guardian of a minor Hindu boy is

Under Section 6(a) of the Hindu Minority and Guardianship Act, 1956, the natural guardian of a minor Hindu boy is the father and after him the mother, and in Githa Hariharan v. RBI (1999) the Supreme Court read "after" as "in the absence of", so both parents are natural guardians. The answer is therefore "Father and mother both". An option naming only one parent wrongly excludes the other, and a grandfather is not a natural guardian under Section 6.