In Luca's grade, $\large\frac{2}{3}$ of the students have a sister. Of the students who have a sister, $\large\frac{1}{2}$ also have a brother. What fraction of the students in Luca's grade have both a sister and a brother?

Question

( A ) $\large\frac{2}{3}$
( B ) $\large\frac{4}{5}$
( C ) $\large\frac{3}{7}$
( D ) $\large\frac{1}{2}$