The “genetics” in Virtual Families are similar to the “genetics” in Virtual Villagers, i.e. what code the program uses to determine which head a new family member will have.
There have been a couple of threads about this already,
here and
hereBasically, if you look at the image files for heads within the game (probably in the folder Program Files/Virtual Families/Images), and number them from top to bottom (1 to 50), the child of any two people in the game will be the average number of their head numbers.
Here is an example of how to number the heads:

This is why most people in VF will have sandy/light brown hair: because those people are in the middle of the heads in the image file – it’s just a question of mathematics. Their number head is the
most likely outcome.
Just think of rolling two dice and what numbers you can get, there are some numbers that are more likely to come out, simply because there are
more ways of making them.
The only way you’ll get a ‘strong’ hair colour that is the same as their parents (such as black or blonde) is if you put two people together with similar hair, and therefore similar numbers on the scale.
Take a look at these examples:


