All We have to care care is Number of Families)F<(number of Girls)G ,G<B
(Number of Boys )B<(Number of Parents)P
1) F = 2 , G = 3 , B = 3 , P= 2 : G<B not satisfied
2) F=3 , G=4 , B = 5 , P= 4 : B<P not satisfied
3) F= 4 , G= 5 , B=6 , P = 6 : B<P not satisfied
4) F=5 , G= 6 , B=7 , P = 10 : All conditions satisfied
Thus Number of families is 5 ... Option 3 is the right answer