There are 8 speaking roles in the play. Of the 8 speaking roles, 5 are for males and 3 are for females. After the 8 speaking roles in the play are cast, the remaining cast members will make up the chorus.

Question

C. What is the probability that the set of siblings consisting of a brother and his 2 sisters are all in the chorus?

My work ( what I did) :

5/8 ... 3/8 so wouldn't you subject the 3 from 5? I am confused