Hummer 2008 H3 Owner's Manual page 36

CAUTION:
{
Never do this.
Here two children are wearing the same belt.
The belt cannot 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.
1-32
CAUTION:
{
Never do this.
Here a child is sitting in a seat that has a
lap-shoulder belt, but the shoulder part is
behind the child. In a crash, the child would
not be restrained by the shoulder belt. The
child might slide under the lap belt. The belt
force would then be applied right on the
abdomen. That could cause serious or fatal
injuries. The child could also move too far
forward increasing the chance of head and
neck injury. The shoulder belt should go
over the shoulder and across the chest.