| Its "disgusting" to us because we've grown up with them. We've gotten to know them as "our brother/sister" Or parent. w/e.
But if we never got those labels, then i dont think anybody would mind.
I dont like it, because i also think like that. But the people who actually do that kind of stuff, either are sick in the head wanting sexual encounters from anybody, OR they are more comfortable with the fact that we're all humans, all related in some way (relations), and a human loving a human is natural. Just without the labels of brother, sister, mother, father | 
