John and his wife have gathered their family together for christmas. they have two sons and each of their sons have two sisters. how many members are there

Okay so this is how I would figure this out: 
John + John's Wife
1 son + 1 son } 2 sons
2 sons + 2 sisters } sons have 2 sisters 
there are 6 people total in their family:
1. John
2. John's wife
3. 1 son
4. 2 son
5. 1 daughter
6. 2 daughter

There are 6 members total.

Hope this helped! :)