Your parents have 2 boys they each have a sister how many children do they have?

The answer is 3. This is exactly like the Mom and Dad have 4 daughters and each daughter has 1 brother. How many are in the family? YOUR question is: Your parents have 2 boys they each have a sister. How many children do they have?

Your answer is 3. Because it's two sons and one daughter. The answer is 3. But if you wanted to find out how many people are in the family ALTOGETHER, then your answer is 5. Because 2+2+1=5. But you're only asking us to find how many sisters the two brothers have and that would be 1.