The boy and girl were in collision with a white Audi A3 car
The PSNI are appealing for witnesses following a serious road traffic collision in Antrim.
Two children are in a critical condition in hospital following the incident on the Staffordstown Road, at its junction with the Greenan Road.
The collision occurred at around 4.40pm on Tuesday.
The boy and girl were struck by a white Audi A3 car, which remained at the scene.
Roads in the area remain closed and diversions are in place.
The PSNI has appealed to anyone who was in the area and who witnessed the collision to contact officers.