More research has been reported lately on the influence of birth order on personality. As described earlier by Frank Sulloway, it seems first-borns are ambitious straight arrows who are steadier, heavier, and smarter than their younger siblings. The latter, however, are more likely to be creative, take risks, and rebel against expectations. I've addressed this here before in interviews with some famous sibs. Saturday morning is a good time for a reprise.
First-borns wear blue. Younger sibs wear red.