More info on this:
It's not the weirdness I thought it was! They're still identical household structures, though -- [i]one[/i] adult female, her teenage [i]daughter[/i], and her child son. And when I went into one to generate a father from the child son, he turned out to look [i]exactly like one of the single male adult townies[/i], no matter how many times I hit Randomize.
So, the game isn't generating nothing but **bleep** families. It's generating nothing but single-mother Sims who've been sleeping with other townies! All their teenage children are female, and all their male children are child-aged (when they first generate: one of the first such families in the list -- I assume that means generated earlier -- the child has aged up and is a teen).
If this is the game creating balance, it's still not doing it right.
