So here's the plot. Fred and George maintain this sort of boy's club network in Hogwarts throughout the four houses where they can exploit various boys whenever they want for sex because they know secrets about them and can blackmail them. They also maintain a business where horny boys or girls can come to them to buy sex with one of their boys. I.e. they're pimps. They got this idea from exploiting Ron for the first time several years ago. Even now they use him regularly at home as a sex slave. However Ron has risen through the ranks of the prostitutes and become Fred and George's second in command.
This is the basic idea and can be taken off from there. I would be Fred and George and you would be Ron and the boys. Basically. Generally I like something a little more plot focused, although this one will probably be quite sex focused. I would like you to post at least once every other day and at least three or four good paragraphs.
I also really enjoy doing flashbacks and this would lend itself well to being one: flashback to the first time Ron was made a sex slave.