I'm a middle child of three. My older sister at first was a way better child than I was. However, after dropping out of college twice, now living at home not able to find a job that pays enough to move out, and not having any passion that I know of whatsoever, I'd say that I'm doing significantly better than her. Not that I don't have my own faults, but my parents were a little too on top of my sister, which caused her to become insecure with her own person, and after a hard break up with a boyfriend of 3 years to develop a series of psychological and eating disorders, which she refuses to see a therapist about.
My little sister has the potential to be better than me, it's not that hard. Be good instead of lucky is all there is to it really. But I guess we will see. The evidence shown thus far is nowhere near conclusive(in terms of my own family).