When you grow up there usually rules imposed on you by your parents, society/community (church, school etc). But doubt anyone here got told or informed "you are not allowed to sleep with family members". That just a given right? Sure when I grew up I was curious of a lot of things, experimented with, and experienced things I both did enjoy and regret, but that is just part of growing up. Neither of this involved any depravity with family members though.
"Depravity" a pretty derogatory word to use on a porn forum...
As for the rest, I think you're taking this a bit too much in a "to the letter" kind of way.
Not everything need to be explained in details, or every rules to be given for a human, even a child, to know what is right or wrong. It's called education, and parents, as well as other institution you quoted, are responsible to educate and make sure the child is able to create a correct morality as he grow.
Take bestiality as an example, everybody know it's "not right" , but I've also never heard about it in school or from my parents either.
it's something you learn on your own.
And everybody grow up differently.
Specially when you reach teenage years and your hormones are all over the place.
Wouldn't be surprised if a boy, when doing laundry for the family, spent ten seconds too long on folding his mom's panty.
Doesn't mean he need to have his brain checked. Just that, unlike what a lot of people seems to believe, love and sex are two different things for humans, love is mostly emotional and thoughts driven. Sexual desire is hormones driven.
You can fuck someone you don't love, you can love someone you don't fuck, and reverse.
In the end it's mostly psychological, not in the meaning that it's a problem, but that everybody can have different world views.
As long as these world view doesn't harm other people I don't really care.
Man, I'm so tired, 10 am for me and I didn't sleep this night... Not even sure what I wrote mean anything, or if it's related to your message, or to the thread subject at all... going to sleep.