If you're looking for anime similar to Yosuga no Sora, you might like these titles. All recommendations are made by Anime-Planet users like you!
Both animes are about a male protagonist finding love with a female protagonist. Also, both animes have the same arc system (2-3 episodes for each individual girl) or in other words, different scenarios. While Amagami is more strictly about the romance and the flower it creates, Yosuga no Sora has ecchi and intimate romance.
Mitsuki and Yuuya have just become step-siblings, and are working to adjust to their new lives as a family living within the same house. While Mitsuki is cautious of this new relationship with her ‘older brother’, her inhibitions quickly take a turn for the perverted when she’s suddenly possessed by Hiyori, a ghost girl with amnesia. As if things couldn’t get any worse, Hiyori forcibly outfits her with a chastity belt that’s so restrictive it often causes the girl to pee herself - not to mention, in order for Hiyori to finally reach heaven, Mitsuki needs to experience a certain amount of sexual pleasure and energy… with her big brother! Now, between trying to not soil herself and trying to get used to Hiyori’s hands between her loins, Mitsuki will do her best to survive her new "family" life with, or without, her virginity intact.
These are both trashy romantic comedies that are heavy on melodrama, light on comedy and have offensively stupid fanserice. Both have a large dose of incest as a major plot point, both have a lot of nudity, although the nudity in My Sister is Unusual is censored in the TV release.
The plots of these anime are quite different. Sora is doesn't have anything supernatural going on, instead it's just the drama that ensures when a brother takes turns romancing and eventually having sex with a group a girls that includes his sister. The anime is made up of seperate arcs where he romances a different girl each time. In Recently My Sister is Unusal, there's a girl that's been cursed by a ghost to wear a chastity belt until she can make her step brother fall in love and eventually have sex with her all for the sake of the ghost being able to move onto the after life. However, the plots in both anime are just an excuse for the fanservice and nudity with romance and story really being secondary.
If you're looking for some heavy ecchi that borders on hentai then these anime are for you. Just be warned that My Sister is Unusual has a weird fascination with urine.