Niece and Nephew
A man was taking his wife, who was pregnant with twins, to the hospital when his car went out of control and wrecked. Upon waking he saw his brother, a relentless world-class practical joker, sitting at his bed side.
He asked his brother how his wife was and his brother replied, "Don't worry, everybody is fine and you have a son and a daughter. But the hospital was in a real hurry to get the birth certificates filed and both you and your wife was out of it so I named them for you."
The husband was thinking to himself, "Oh no, what has he done now?" and said, "Well what did you name them?"
The brother replied, "I named the little girl Denise."
The husband said, "That's a very pretty name! What did you come up with for my son?"
The brother replied, "Denephew."