GMC 2002 Envoy Owner's Manual page 67

CAUTION:
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
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 sitting in a rear seat
outside position, see "Rear Safety Belt Comfort
Guides" in the Index.
-
shoulder belt,
1-55