Ashton Kutcher has discovered a strange side effect to his relationship with older girlfriend DEMI MOORE - he has developed paternal instincts towards her children.

Although at 27, Kutcher is only ten years older than 42-year-old Moore's eldest daughter with her ex-husband Bruce Willis, Rumer, 17, he insists he behaves fatherly towards her - most notably when she asked to bring a boyfriend to the set of his MTV show PUNK'D.

Kutcher says, "I couldn't stand the guy before I had even met him. I've already begun to develop these protective, fatherly instincts."