Has anyone actually had kids while playing this game, and then managed to get those same kids playing seriously?

YES/NO

MAYBE

...?

I don't have statistics or names but I would imagine so, yes.
A kid of 5-8 could play this game and war.

At least one of the best netgainers in the history of this game was a preteen when they started playing. Well unless it was a joke, but it was repeated often enough not to be.

The game goes back to at least 1998. So 13 years give or take some months.

I guess it all depends how serious. Way back when I am sure many people had parents, siblings, aunts, uncles, friends (both real and imaginary), pets, inanimate household objects, plants, and zombies so I am sure some had children playing too.

some have been during years, no idea if any parent+kid combos atm.

my step father got me into this damn game when i was 10 or 11... 12 years ago

martians only clone.. no kids:P

I know of one parent/kid combo, but the kid was born before he started playing.

It would be hard to play from the womb.

I've had a couple of my kids play from time to time. They were all born before I found the game though.