Dont forget the tweeners. We all love Rob and Laura Petrie, but Richie was pretty much left to be raised at his friends houses after the first season, so the Petries could pal around with Buddy and Sally more.
Rob and Laura Petrie was the brainchild of Carl Reiner writer and actor in Your Show Of Shows. It was his story. But the network wanted a more popular face so they hired Dick Van Dyke. (Reiner appears regularly as Alan Brady whose comedy show Rob wrote for)
Had they done the real story of Carl Reiner it would have shown Richie morphing eventually into Rob Meathead Reiner. None more progressive than he.