Heh - we blame ourselves... Child #1 as a toddler we followed him around, made sure he didn't get hurt climbing anything, picked him up immediately when he fell, coddled him, etc. - I think anyone with their first knows what I mean... By Child #3 we would watch him climb stuff, play hard, get hurt, get up, but we didn't move a muscle unless we saw blood. OK, not that bad, but again he had far more opportunity to become coordinated. There are within 5 years of each other and I'm sure that helped on the opportunity side...
By the time #3 was old enough to be on a team he understood the game and was making plays other kids his age weren't (one unassisted triple play - catch, touch base, tag following runner). We believe this was mainly because he'd been around his older brothers watching and learning. Sports/Athletic jealousy raged from the older ones of course, but things levelled out over time. Eventually hard work and natural ability have a crossing - if you don't realize it, you get left behind. #3 ended up playing d2, but only 1 full season... In the long run academics and a shoulder injury did him in. #2 played HA d3 all 4 years, went on to law school, and is a successful lawyer in NC. #1 played 1 year at a HA d3, decided he'd rather focus on school. He used his ability to get into a school he may have been on the edge of getting into without it. He's a successful grinder in many ways. It took #3 a few years to get on his feet and find a passion, but he's seems on the path now.
So yes, I agree the youngest was the most talented athletically early on and certainly looking back I believe that had a lot to do with opportunity and watching. Having watched other similarly situated families in our social circle I saw many with similar dynamics athletically.