If you're looking for manga similar to Kiss x Sis, you might like these titles. All recommendations are made by Anime-Planet users like you!
Haruka is a sweet, innocent high school girl who is very excited to meet her new step-brother, Tsukasa. Since her father works overseas, Haruka has been living alone, but now that her father has remarried, she'll have little grade schooler Tsukasa with her while both their parents are out of the country. When they finally meet, Tsukasa is even cuter than Haruka had hoped! He wants to get her help with his homework and sleep in her bed...and undress her and make love to her!?
Ono Matori is a high school student who is secretly a successful erotic manga author. He has recently found new inspiration for his work from his neighbors and classmates, the Hikasayama twins, Haruna and Wakana. Both Haruna, the cheerful and active half, and Wakana, the cool and collect one, both fall in love with Matori. He unwittingly agrees to date both of them both for research purposes and personal interest. Their love triangle will help Matori with his erotic manga storyline but how will his life change back in the real world?
These two manga have a similar type of comedy and similar dynamics, along with incestuous relationships. Let's say that in both sides we can admire the relationship between the male lead and a couple of cute twin sisters in love with the same person. Oh, let's not forget the huge amount of sexual content and nudity.