Also I'm pretty sure four adults can't file a single tax return together?
This^^^.
At least for tax purposes a household is anyone that is paying taxes separately, as far as I know. So a single mom with two kids would be a household. Throw in a dad and it becomes a family. I could be wrong though. I don't think four people with 60k incomes renting a house would be considered a household. And in any case if you are single and making 60k, and not living in NYC or SF, you are fairly well off.
Still....depending on how you define a middle class lifestyle Romney is kind of right. Even the Democrats don't want to raise taxes on anyone making less than 250k. Is the upper middle class not middle class?