I can't rember their exact ages, but I had a couple both in their early sixties when a three-year-old turned up at the door. Their other kids were all off at college by then. They both died after five or six years and I opted to move to the next generation, where the kid grew up automagically to be in his twenties.
It did cross my mind to leave him in the house alone, but I'd tried that with another kid in another game; when I saw how depressed he was I had felt it kinder to start the next generation.
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To err is human; to arr is pirate.