Firstborn Children Smartest?

According to a story in today’s S-R a recent study confirms the long held belief that your big brother/sister really IS smarter than you.
Scientists found the IQ’s of firstborns were two to three points higher than their younger siblings. They surmise “that older children are showered with attention early in life and treated as leaders within the family…”
Great. My firstborn already thinks the rest of the family, especially his parents are idiots. Now he’s got ammo.
What say you?
Are your firstborn children smarter than than their siblings?