It's a loaded question, of course, and carries with it all sorts of presumptions, which - in my experience - are not generally true. Even so, when asked this question I usually answer, "Their parents."
As one piece of evidence for my answer, consider this story (it's a bit old, I know, but I've been otherwise occupied) about the cancellation of an Easter Egg Hunt in Colorado Springs because of the behavior of the parents:
Parenting observers cite the cancellation as a prime example of so-called "helicopter parents" — those who hover over their children and are involved in every aspect of their children's lives — to ensure that they don't fail, even at an Easter egg hunt.
"They couldn't resist getting over the rope to help their kids," said Ron Alsop, a former Wall Street Journal reporter and author of "The Trophy Kids Grow Up," which examines the "millennial children" generation.
"That's the perfect metaphor for millennial children. They (parents) can't stay out of their children's lives. They don't give their children enough chances to learn from hard knocks, mistakes" [more].Parents, please don't ruin your children's fun by being obnoxious.
Capello tip to Deacon Kandra.