Family Math

Just filling some time today passing along this li'l algebraic Friday puzzler that Richard Wiseman offered last week (I've re-stated it slightly):

In a certain family with 2 or more children, each daughter has the SAME number of brothers as she has sisters, while each son has TWICE as many sisters as brothers. How many sons and daughters are in this family?

answer below:
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answer:  4 daughters & 3 sons