There is a strong link between individual height and economic and educational success, in part because height reflects childhood nutrition that also affects cognitive development. Research by Anne Case (Princeton) and Chris Paxson (Brown) shows more success, remarkably, even for taller relative to shorter siblings. Aside from random genetic variation, moms do not necessarily give the same size piece of apple pie to each kid.
There is no data on apple pie slices, of course, but there is data on whether moms got prenatal care and smoked or drank during pregnancies. Good behavior varies between pregnancies even for the same mom, which affects birth length and weight, which affects height, which affects success.
I'm a little touchy about this line of research as a 5'8" male raised on Captain Crunch and TV dinners. The more serious development point is that improving early childhood nutrition has a huge payoff because it affects lifelong individual success.