Pontiac Montana SV6 2007 Owner's Manual page 56

CAUTION:
{
Never do this.
Here two children are wearing the same
belt. The belt can not properly spread the
impact forces. In a crash, the two children
can be crushed together and seriously
injured. A belt must be used by only one
person at a time.
56
Q:
What if a child is wearing a lap-shoulder
belt, but the child is so small that the
shoulder belt is very close to the child's
face or neck?
A:
If the child is sitting in a seat next to a window,
move the child toward the center of the vehicle.
If the child is sitting in a center rear seat
position, move the child toward the safety belt
buckle. In either case, be sure that the shoulder
belt still is on the child's shoulder, so that in a
crash the child's upper body would have the
restraint that belts provide. If the child is sitting
in a rear outboard position, see Rear Safety
Belt Comfort Guides on page 51.