Could you please explain the question below?

Question

In the Logan family, each daughterhas the same number of sisters as she has brothers. The daughters, incidentally, are all older than the sons. How many sons and how many daughters in the Logan family?

Thank you.

Answer 1

Let D=number of daughters in the family.
Number of sons = D+1
We also know that D>1 by virtue of the sentence:"The daughters, incidentally, are all older than the sons."

So the total number of offsprings in the Logan family is D+D+1=2D+1 where D≥2.