The height paradox is that those 5'7" guys who lost two inches staying up all night and drinking soda as teens but got their shit together as adults would go above and beyond to make sure their sons ate healthy and good a good night's sleep, but unfortunately the odds of having any has already been dramatically reduced.
Part of the role of uncles is that it's a wider net that can provide these kinds of examples, in a casual "Hey, take it from someone who's made those choices" kind of way.