CP calculations differ in all states. In VA, where my daughter's father lives, they added what the two of us make a month, took a percentage of that as to what we would spend on my daughter each month, then added daycare and some crazy medical/dental amount of $11. This gave them a grand total of what she "supposedly" costs per month. He pays a percentage and I pay a percentage.
I don't know if the fact that he makes more than me had anything to do with the percentage that he was ordered to pay or not. Subsequent children have no bearing on CP at all - only his income. They will not include his wife's income (if she had any) nor with they consider the fact that he bought his father (or did you say he bought HIMSELF -either way doesn't matter) a new house. Obviously he makes good money if he supports a household on his own and could afford a new house.
Some states have more complicated calculations than VA I'm sure. You would have to check with an attorney who might know for sure in your state/county.