When Steve reminisces about the time Chip as a child had a girlfriend Chip Off the Old Block (1960), he says "the boys" teased him about it. The thing here is that that would have included Mike ( Tim Considine ) as one of the sons, but after a couple of mentions early in season six, Mike was never acknowledged again and completely removed from the show. In fact, there are several times in the later seasons where Steve refers to Robbie, Chip, and Ernie as his three sons, completely ignoring Mike.