I blame the show The Brady Bunch for today's societal problems.
Why were Carol and Mike single in the first place? This is an unresolved problem
What happened to their original spouses? It's like the mother of the boys and the father of the girls never existed. Did they die and were so easily forgotten? Was there a divorce? If so - how come the kids never went to visit the other parent? Did the mother of the boys and the father of the girls just run away? Was there abuse? Was that why the other parents were never mentioned? The family's little secrets?
Maybe Mike and Carol killed their original spouses so that they could be together. The Brady parents fit the bill for serial killers. Quiet - kept to themselves. Was Sam the butcher involved in the disposal of the bodies?
When you look back on it - the complete lack of other parents in the show is very creepy.