I love seeing portrayals of complex family bonds, especially mother - kids in fiction. Whether that's complex good or complex bad, whether it's a family who are divided against each other or who are loyal to each other above all else. I love seeing it in a wholesome, nurturing way, where they stick together through thick and thin, or reconcile their differences, or have a moment so touching it moves me to tears.
And yet, I have no problem sullying a beautiful and sweet dynamic like that in fanfiction, and putting them through absolutely gross and sicknasty sexual mishaps. That's the thing about being proship, and being able to distinguish fiction from reality (and fanworks from source material). The wholesome and the revolting can and do coexist and are enjoyed in their own ways.
It's like quantum physics (not that I know how that works). The same place at the same time, in different states.