Pontiac 2003 Bonneville Owner's Manual page 35

Never do this.
Here two children are wearing the same belt.
The belt can't 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.
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 the center rear seat
passenger 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 so
small that the shoulder belt is still very close to the
child's face or neck, you might want to place the
child in a seat that has a lap belt, if your vehicle
has one.
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