Sims 2: Extra Thumbnails?

I made two adult sims and played them. The wife got pregnant and had twins. I saved and continued playing. I saved and quit aftter a couple of sim days, but the twins hadn't grown into toddlers yet. The next day (in real life) I went back on to play the family and the twins had each gotten and extra thumbnail on the left where it shows the family. There aren't extra babies though. Just the twins.