Shimrod talks about the family configuration problem at length on his mod page. It would appear that the game chooses the single mom-teen-child family 95% of the time and ignores other game-defined family configurations, for the most part. A lot of folks don't care for the configurations he came up with to replace that one, but if you read his analysis maybe someone can come up with other configurations they like better. Maybe there can be different "flavors," the way Tanja1986 has done with her alien abduction/pregnancy mods, to suit different tastes.
http://modthesims.info/d/548447
ETA: I use the mod, myself. I'd rather have what he came up with than what the game sticks us with, but I'm open to other possibilities as well.
