Bad storm

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 "Mummy, will you sleep with me tonight?"

The mother smiled. "I can't dear" she said. "I have to sleep in daddy's room".

The little boy replied with a shaking voice

Spoiler:

"The big sissy".