I dont understen how can be incest and netorare at the same time?
There is only one man and only one woman. So is mother and son? Or Dad and dughter?
In both cases there is not realy netorare.

So can explain to me?

Also if you go on this site in the synopsys there is not netorare, but only incest.
http://www.dlsite.com/maniax/work/=/product_id/RJ084907.html

Base +9, nurax +10, Xcel -9, Palaxius -30, k1bell -6

it's his aunt, she is married to his uncle,so netorare

Base +7