Solution

The age of the second eldest person is 70 year which means the age of the grandmother is 70 year. T is the brother – in- law of M. T’s age is 2 year less than M’s age and M’s age is 6 year less than Q’s age. P is the mother of Q and her age is 2.5 of the age of her son. From these it is clear that M, T and Q belongs to second generation and P is the grandmother whose age is 70 year. Further, only the father of R is sitting between O and T. R does not belong to third generation. So, R belongs to second generation. The person who is sitting on the immediate left of M and immediate right of P is 18 year old while O is 10 year old. Q, who is sitting next to O, is not sitting opposite to M. O is the female member of the family. O is 10 year old. So, O is the granddaughter and 10 year old. P is 4 year younger than N. Means N is 74 year old. Rest S’s age is multiple of 4 but not a perfect square. As only remaining position is that S is the grandson and is 12 year old. The person who sits immediate right of T is a male but he is not S.. As we know that S can’t sit between P and M, so clearly R sit between P and M and S can’t sit to immediate right of O so from this case 2 will be eliminated. Rest we know that the age of R is 18 year so she is the daughter of N and Q is the son of P and is 28 year old. Rest T is 20 year old, M is 22 year old, M is 22 year old.  So, the final arrangement is –