Duuude, child support is so complicated.
Here, as far as I know it's "household" income. Meaning, if mom and dad are split from each other and living with new partners, the new partner's income counts, regardless of marital status. Also, household size counts- if that new partner has kids, that means something, too.
Which I understand, in a way- if you got yourself a SugaMamaDaddy, why do you get to say, "Oh, I have no income," just because you aren't
Still, though... super complicated.
In the case of DSS's other parents (mom and stepdad), they make more money than we do. But they live in a higher COL area. All things being equal, they probably have a higher net income than we do, but only because DSS's mom works and I SAH. But we have more kids- one part time, one full time, and one on the way, vs. just DSS for them. There are just so many variables, it's impossible to compute.
When we (and I mean all four of DSS's parents) were trying to get CS through friend of the court, we were given pamphlets that just said, "These are hard issues". Gee, thanks, that really clears it up.
Thank God, everyone concerned is reasonable. We decided to keep it out of court, and negotiated our own thing- we pay for DSS's braces, college (fully funded! yay!) including books and car and room and board, any remaining medical expenses after insurance, as well as smaller incidentals like school clothes and activities and so forth. And if they need money, all they have to do is ask.
Not that this is here or there for your situation OP, but it's so hard to figure it out that you probably won't be know until you go before the judge. I'm sorry, 'cause that sucks.