Cute joke

One summer evening during a violent thunderstorm
a mother was tucking her small boy into bed.

She was about to turn off the light when he
asked with a tremor in his voice, "Mommy, will
you sleep with me tonight?"

The mother smiled and gave him a reassuring
hug. "I can't, dear," she said. "I have to sleep
in Daddy's room."

A long silence was broken at last by his shaky
little voice: "The big sissy."