6 Teenagers, each matched by age, no blood relation, ... if it was 'Only' Greg and Marcia doing that, it'd be more shocking...
I know it was a 'simpler time' but the whole 'Greg and Marcia share the Attic' Episode at the end of Season 4 seemed down right Naive all things considered...
- lets but the Two pretty 17 year-olds in one room, as far away from the rest of the Family as possible