The paranoid in me wonders if they had a second set of "clean" phones that they could use to arrange their mischief.
The not-yet-a-parent in me hopes that they did, especially since they seemed to be doing fine otherwise.
1a - If kids misbehave badly enough, can't the parents get in trouble instead / as well?
1b - But, aren't married couples (sometimes?) responsible for eachother's debts?
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2. Who's responsible if [the person being watched] gets hurt?
2a - Parents are definitely responsible for keeping kids safe, and I've heard they can sometime get in trouble for not watching closely enough even if nothing happens.
2b - Married people tend to be adults, and considered responsible for their own safety and wellbeing.
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I'm guessing the different standards have something to do with (2).
You simply can't have it all; you can't raise children in a free-flowing environment where they can explore and learn from the consequences of their own actions, and throw parents in jail for hypothetical things that could have gone wrong because they weren't being helicopter parents. Which is damn near legally mandated now. Or at least, what is legally mandated would have been considered helicopter parenting when I grew up.
I say this without comment as to the right balance for society. I just wish there was one that I could rely on it.
No pun intended: why you married her?