Post a character who is in love with as well as has an attraction to and at the same time has an unhealthy affection and love for/towards his/her sibling (including twins). Overall a character who has an unhealthy sibling relationship

Hikaru and Kaoru

Belarus... Russia's behind the door, and anything that stands between them will die. Not a threat, a warning.

Utau from Shugo Chara...she eventually outgrows it though, so I'm not really sure if it counts.

Lelouch & Rolo (Code Geass R2)

Rolo is not his real brother of Lelouch but they became brothers......and rolo is sooo attached to his brother .that he want him for himself..if anyone tries to love Lelouch he will kill them in an instant.......even though Lelouch used him as a tool....rolo was happy to be his brother knowing he was just a tool....when Shirley who loves Lelouch more rolo killed her in an instant.....and Lelouch gave rolo an order to protect his loving sister nunnaly.but instead Rolo was going to kill her.soooo he will get Lelouch for himself.......but his plan failed........but the last moment of Rolo was touchy......he saved Lelouch from the whole army with his time stopping gias power..but as cost of using tooo much gias power Rolo died by saving his brother...........

Namie Yagari for brother Seiji (Drrr)

Who else but Keita Sumione and his 2 sisters?
Show: KissXSis

Maguro Kurokami! The room has A LOT more

Hiromi Nase from Kyoukai no Kanata has a sister complex... And I don't know how or why but somehow it doesn't feel that weird or perverted to me...?

Mikasa and Eren. (Attack on Titan) (Hope this counts, seeing that they aren't truly related) Though it's so Mikasa's obsession with Eren (which is very prominent in the chibi specials, lol) She's quite brash and dangerously impulsive when it comes to him.

I'm not too sure if they're meant to have a romance, though. :|

Miki and Yuu from Marmalade Boy

This show is like a soap opera and it is pretty addicting once you get into it. Miki and Yuu's parents get a divorce and end up marrying each other's parents. The parents decide it is a good idea just for all of them to live in one house... yikes... but there really aren't any hard feelings- which is weird.

Miki and Yuu end up falling in love but decide to hide it from their parents. Then through a series of events, they think they actually might be flesh and blood siblings but they decide that they already love each other so it doesn't matter. It's complex.