At the end of the first arc, Kaname turned Yuuki into a vampire, revealing her true nature as the pureblood princess of the Kurans. It was said that Yuuki was born as his sister and his future wife. However, it was later explained that Kaname was not Yuuki’s real brother, but her ancestor who was awakened at the cost of her real brother’s life.
Sorry, but I still like this pairing better than Zero x Yuuki, and Rainer and Rieyn both look stunning as the pureblood siblings! I think the ending of the manga was rather tragic and I felt that it was a little rushed somehow! I think I will keep the anime ending in mind instead of the manga. Thanks again to Orangish for sending this in!
Source: Rainer on Weebly