I did, a couple years ago, start a darkfic (now completely abandoned, seriously never touching it again) where Aang had been killed and Azula was BWAHAHAing across the countryside, and Katara knew the Avatar would be reborn in the Water Tribe and thought he would choose to be reborn close to people who had loved him, and her brother was the only Water Tribe guy in the area (wasn't like she could ask a guy from another country, what if the kid ended up the wrong kind of bender to become the Avatar?) Anyway, she was desperate and in pain and feeling guilty over not saving Aang and in HUGE denial that there's nothing more to be done, and Sokka tried to tell her it was crazy but well, he'd do just about anything for her, even when he knows it's a horrible idea. In the end I never decided whether anything did happen between them, or if Sokka stopped it before it could go that far, but I know afterwards he points out that even if they get the Avatar back he still would not be *Aang*, and then she breaks down.
I dunno, I really liked the dynamics in that story, all entangled together in bonds that aren't necessarily comfortable or positive, but still unbreakable, and having all that huge history with some really bitter parts, but loving each other no matter what, even if they do some things they might never forgive.
Anyway, culturally it worked because it was a really dystopian fic. I think this is a pairing that tends to work better when they've lost even their village or are really far away and cling to each other because they're the only thing accessible/left of their past. Though hey, with such a small village as the Southern Tribe has got, I bet they don't have much choice but to allow first cousin marriage, and considering Katara seems to be the only teenage girl and the last waterbender, she'd have to get married at some point if they'd never left the village. Dunno. *ponders* I get the feeling you could do something with that, but I'd have to think about it more to figure out the specifics, because in general cousin =/= sibling.
Re: SOKKA >:O
I did, a couple years ago, start a darkfic (now completely abandoned, seriously never touching it again) where Aang had been killed and Azula was BWAHAHAing across the countryside, and Katara knew the Avatar would be reborn in the Water Tribe and thought he would choose to be reborn close to people who had loved him, and her brother was the only Water Tribe guy in the area (wasn't like she could ask a guy from another country, what if the kid ended up the wrong kind of bender to become the Avatar?) Anyway, she was desperate and in pain and feeling guilty over not saving Aang and in HUGE denial that there's nothing more to be done, and Sokka tried to tell her it was crazy but well, he'd do just about anything for her, even when he knows it's a horrible idea. In the end I never decided whether anything did happen between them, or if Sokka stopped it before it could go that far, but I know afterwards he points out that even if they get the Avatar back he still would not be *Aang*, and then she breaks down.
I dunno, I really liked the dynamics in that story, all entangled together in bonds that aren't necessarily comfortable or positive, but still unbreakable, and having all that huge history with some really bitter parts, but loving each other no matter what, even if they do some things they might never forgive.
Anyway, culturally it worked because it was a really dystopian fic. I think this is a pairing that tends to work better when they've lost even their village or are really far away and cling to each other because they're the only thing accessible/left of their past. Though hey, with such a small village as the Southern Tribe has got, I bet they don't have much choice but to allow first cousin marriage, and considering Katara seems to be the only teenage girl and the last waterbender, she'd have to get married at some point if they'd never left the village. Dunno. *ponders* I get the feeling you could do something with that, but I'd have to think about it more to figure out the specifics, because in general cousin =/= sibling.