Chevrolet 2007 Avalanche Owner's Manual page 44

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.
44
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. Also
see Rear Safety Belt Comfort Guides on
page 38. 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.