Explanation:

Reference: Eight persons  Sarin, Rahi, Akasa, Pavi, Preet, Gunjan, Taran and Namya belongs to a family which consists of three generations and two married couples.
Inference:We will keep this information mind while solving the puzzle.

Reference:Preet is the sister of only son of Akasa.

Rahi is the mother of Akasa.

Inference: After using the above hints, we can draw a following blood chart:



Reference:Sarin is the grandfather of Taran who is the daughter of Pavi.

Pavi is the daughter in law of Sarin.

Inference:After using the given hints, above blood chart can be redrawn as:


Reference:Namya is the maternal uncle of Gunjan.
Inference:With the help of above hints we can say that Namya is the brother of Pavi and Gunjan is the son of Pavi.


Following the final solution we can say that Akasa's son is grandson of Taran's grandfather.