I attached two images hopefully they are helpful. the first one I sectioned out so you can see the different generations and that there are only three. in the second image I circled in green the two mated pairs. you can tell they're mated bc they are connected by a horizontal line. the vertical line that descends from their connection branches off to more circles and squares (females and males), which are their offspring and a new generation. the affected pairs are the ones that are colored in red. there are 2 squares and 1 circle in red (2+1=3). hope this helps