You go to the Images folder in the Virtual Families game folder found in Program Files. The image you need to look at is bigheads00.png

Once that is open, find the mother's and the father's head and count how many heads are seen in between them.



I counted 64, so half would be 32. The heads closest to the middle will most likely be the kids!



If you happen to get any other kids that show up between the parents or one spot above/below them, they're naturally a part of the genetics and not a rare child.