Derived from "win" and "incest".
As opposed to more common forms of incest where abuse is common, wincest must include both sibling and romantic love as well as mutually consensual sex.
As a result, wincest is almost exclusively between brother and sister, and not between parents and children. A related term, twincest, requires that the siblings be born as twins.
Not all incest is wincest, and not all wincest is twincest.
Wincest is win, but twincest
is twice the win.
Cousincest can't be wincest because it's not incest.