Yes. Siblings who are on the wait list are placed in the 'Sibling Priority' group. For intake years (Cottage, Kindergarten and Year 7), if a sibling is on the wait list prior to the conducting of enrolment interviews for that year group, then it is usual that they will be called in for an enrolment interview before those on the general wait list.
A sibling is not necessarily guaranteed a place, as this is dependent on a successful enrolment interview, but it is usual, in most cases, that an offer of enrolment is extended. In cases where a sibling is not on the wait list prior to the commencement of the enrolment interviews for that year group, they will still be placed in the 'Sibling Priority' group, but the scheduling of their enrolment interview will be dependent on when the next place becomes available.