Drawing the Family Tree as per the given information:
Let the "Daughter" be denoted by "d" and "Son" be denoted by "s".
From the Given equations:
Each son had the same number of sisters as he has brothers and each daughter has two times as many brothers as she has sisters,
We can form the Two Equations:
(S -1) = D → i)
2 (D - 1) = S → ii)
Now putting the value of equation i) in equation ii) we get,
2 (S - 1 - 1) = S
2 (S - 2) = S
2S - 4 = S
S = 4
number of Sons = 4
Now we will put the value of S in equation i) we get:
(4 - 1) = D
D = 3
The number of daughters = 3.
Hence, the correct answer is "3".