My five year old has the biggest urge to feel important and is always trying to get attention and validation, ?

Even from strangers in public. He is my youngest of five and I've never seen any child feel the need to be so important. My others are grown...not in the home, except for one. My five year old has a very typical life for a kid, and is not deprived of stuff or attention, but quite average in those things. Why might he want to be so super extra important, like he has the ego of a thirty year old or something. He's very playful otherwise. But he's bossy and self important far more than most his age. Any idea why?