Kuro to Kin no Akanai Kagi.

Both deal with the brother - sister type relationship, romance and have smut scenes. Main difference is that Yosuga no Sora is a harem, while Kuro to Kin is reverse harem .  

Both are examples of on screen sexual intimacy involving unhealthy relationships that is not grossly exaggerated (physically at least). The MC in both are girls with brother complexes, and the story revolves around the drama this leads to. Whilst Kuzu no Honkai is longer, with more character exploration, it doesn't distract from the vacuity; if you are after a similar show in terms of cheap softcore pornservice/artistic sexual intimacy (depending on how you look at it), this is the show to go for. 

Both Involves romance, smut and revers harem  

Both anime are about the love story of a brother and sister relationship. The difference between the two: Oreimo 2 is a Harem while Kuro to Kin no Hirakanai Kagi is a Reverse Harem. 

Kuro to Kin no Akanai Kagi and Koi Kaze have in common: ~love story between brother and sister ~jelousy/drama/conflicts ~sexual acts ~both are mature and should not be watched by people under 17 years While Kuro to Kin no Akanai Kagi is adapted in 2 OVA's of 29min(the story might go too fast or have plot holes), Koi Kaze's story is explored wider, in 13 episodes (24min). Difference is that Kuro to Kin no Akanai Kagi is a reverse harem and Koi Kaze is seinen. 

Both are based off of Otome games. Kuro to Kin is more mature content than Diabolik Lovers, but still good.  

Both seem to be the type of hentai that girls would enjoy; Although Lovely Day is a whole lot more smutty and involves more action. 

Both feature a yandere character and have supernatural elements. Both are reverse harems. 

Both stories are about love between two siblings aka incest, especially with the brother trying to hide his feelings for his sister.