Disclaimer: I own none of these characters.
There are times when Kankuro wonders if he has a death wish. After all, sleeping a sibling is one of the most taboo acts one could commit. The fact that he is sleeping with his male sibling bumps it up higher of the list of taboo acts. But that's only part of it. The most dangerous thing about sleeping with his brother is the fact that his brother is a homicidal, emotionless maniac who has no qualms about hurting someone, even his brother. Especially his brother.
But even though it's dangerous, Kankuro keeps doing it. The feeling is addictive. He loves watching writhe on his sheets, pale skin flushed and damp. He gets that reaction a lot; he's a puppeteer, he has to be good with his hands. And he is. He knows exactly which finger to move to get a certain movement, exactly which movement to get the desired reaction. And Gaara never disappoints.
The first times he actually penetrates Gaara, Kankuro is scared shitless, eyes flicking rapidly between his brother's face and the gourd propped against the wall. He keeps his ears pricked for the slightest rustle of sand because he's done this with other boys and of course he knows how much it hurts. That first time is one of the nerve-wracking experiences of his life. Every rustle of sand sets him on edge and afterwards he has no idea how he actually managed to get through with it. The following encounters are almost as bad but now he ignores the ominous shifting. They both know that even though Gaara rules over Kankuro and Temari by day and most nights, Kankuro is the one who rules these encounters.
Perhaps why he lets Gaara into his bed, Kankuro muses. He loves the chance to be in charge, especially after the years of torment. Gaara can't hurt him while they are doing it because then he wouldn't have anyone to go to. Kankuro is the only one willing to take the chance. Sometimes Kankuro wishes Gaara had another reason for not harming him; sometimes he wishes Gaara actually cared for him. But he knows better. Gaara loves only himself.
But he'll take what he can get because years of living with Gaara have taught him to be thankful for any moment Gaara isn't intending to hurt him. And so he'll let Gaara crawl into bed every night, he'll touch Gaara in the most sinful way and he'll possess Gaara the only way he can.