It's... Yeah, pretty weird, at least. I think it's supposed to have to do with promoting attraction to compatible partners and reinforcing certain genetics, but family that grows up together usually experiences something called the Westermarck effect which inhibits that sort of attraction between very close relatives.

[He sighs, arm still over his face.]

What really sucks is knowing all of this and being adopted, so you're just super paranoid about dating until you're sure you're not long lost siblings or something.

[His life is a struggle.]