Also, from what I read, you said you went to "start a new game" to create a family. Did you save your game at any point with your last family? If you did, you should be able to see that save at the main menu, so they're not lost. However, if you didn't save you probably lost all of your progress up until that point. But, that doesn't mean that the family is totally gone.
If you created the family yourself, they will still be in the Family Bin unless you deleted them yourself. You find this bin by starting a new town and instead of entering Create-A-Sim, you click the button that says "Move In Household" (something to that effect, anyways). You'll find all of the families you've created, plus a few pre-generated families that came with the game. Your families will be in front, starting with the one you created last and going backwards chronologically.