Counting Siblings

Since john has 2 brothers so there are 3 male children. Now if all of them have one sister, then there must be only female child who is the sister to all three. Since we are asked the minimum no. Of children in the family, it is 4

The absolute minimum is 3. While John is traditionally a male name it the problem doesn't specifically state that (s)he is male.

But it says John is a child John COULD be a girl with very strange parents which would mean there are only 3 children.....................

So we start out with knowing that we need to add 1 to the number of siblings John has. So we can start solving.

Step 1: Figure out number of brothers. The answer to this step is already in the information. John has 2 brothers.

Step 2: Figure out number of sisters. It says each brother has 1 sister, this doesn't mean the 1 sister is different for each brother. So since we need minimum number of siblings, we should take that there is a "common" sister for both brothers. So there is one sister.

Step 3: Conclusion. Now we add up the information - John + 2 brothers + 1 sister = 1 + 2 + 1 = 4.

4 Children