Melty Drop is releasing a new drama CD series called "Kindan no xx Ai" / 禁断の××愛CD. No release date and seiyuu cast yet but they described this series as 「究極の愛」をつめこんだ禁断恋愛シリーズ! (The extreme forbidden love series!)
It comes in 2 CDs, which shows MC's struggle to choose between the 2 guys. Melty Drop produced 'Aisaresugite xx sarechau' series, so I think this will most likely be r18 as well.
Vol.1 Forbidden love with your older brother & younger brother.
Price: 2000yen+ tax
From what I understand according to the CD descriptions here, basic plot is: your protective older brother (stepbrother from parent's 2nd marriage) has feelings for you but kept it a secret, until your university kouhai shows up (who happens to be your blood-related younger brother separated at childhood but you both forgot) and you started dating. Who will MC choose in the end? Each CD has a different ending.
It sounds like a complicated drama so I hope they cast really good seiyuu for this volume. I also got a bit confused because they described the scenario dramatically in the official site, so I had to ask Japanese friends & fellow Japanese language learners. If you see any mistakes, please feel free to correct me ( ´ ▽ ` )ノ. With that said, I can see a trend for kindan/forbidden/incest love plot starting!!