At present,Tanay's age=9

Age of tanay's cousin= 12

Age of tanay's sister= 14

After 20 years of Tanay's birth,Tanay's age=20****(9+11)****

Age of tanay's cousin= **12+11=23**

Age of tanay's sister= **14+11=25**

After 20 years of Tanay's birth, double of the sum of ages of Tanay's cousin and Tanay's sister=2(23+25)=2(48)=**96**