Only Siya belongs to the first generation.Hence option C is correct.
In a family of 8 members, there are only two married couples and only married couples can have child.
Shikha is the elder sister of Sahu, who is married to Siya.
Salvi is the daughter of Sumi, who is the nephew of Shikha.
We will always keep the first hint in mind while solving the puzzle.
According to the first hint, in order to be the father of Sumi, he must be married to someone. Thus we get our two married couples as shown below.
Siya is the grandmother of Sara.
Sahil is the brother-in-law of Shri, who does not belong to the first generation.
It is to be assumed that wife is younger than his husband.
With the first hint it is clear that Siya is female and also Sara is male because only Sumi is the married person from second generation and Sumi has only one daughter who is Salvi. Thus Sara must be Sumiâ€™s son.
As Shri does not belong to first generation, so Shri must be the wife of Sumi and thus Sahil is the unmarried brother of Sumi in order to be Shriâ€™s brother-in-law.
As per the last hint, Sahu is older than Siya and Sumi is older than Shri.