When this runs you would get for each trial:
Child 1: X + (X or Y)
Child 2: X + (X or Y)
Child 3: X + (X or Y)
Child 4: X + (X or Y)
Child 5: X + (X or Y)
Well in this scenario we would be looking to see if the gender of the 5 children is going to be a girl or boy. Depending on the situation there is a 50/50 chance you get a XY or XX combinations which determine the gender.
So if the couple plans to have 5 children we would run a simulation that would randomly generate either a X or Y and add it to an X for 5 children. This would be done 120 times to get the desired amount of trials.
Each (X or Y) would be a 50/50 chance probability meaning 1/2 chance to get X and another 1/2 to get Y.