*sigh* here is the rundown on the VF genetics as i understand it.
if you have the PC\MAC version, you can go into the game files and look at the file ' bigheads00 ' (or you can just refer to this..)
this will show all the heads that are in the game.


those 2 pictures create the single file.
now! please refer to the picture below.

now as you can see, these two heads are towards the bottom of the file. now! the two circled heads are the two adults that have been married. they are most likely to have the heads between, beside, or their own, as their children!
now!
if they have one outside of that range it is considered a rare person.
Thats all! Questions?