Alexei

Alexei is one of Diva's chevaliers who appear only in the manga. The character is based on the historical figure Alexei Nikolaevich of the House of Romanov, the youngest child and the only son of Tsar Nicholas II and Tsarina Alexandra. He was the heir to the throne of the Russian Empire.

Blood+ Adagio
Alexei inherited hemophilia by birth from his mother Alexandra. He had to be careful to not injure himself because he lacked the clotting factors necessary to prevent him from bleeding to death. His disease led to gossip that his mother was having an affair with the starets, Grigori Rasputin. Rasputin claimed to be able to "heal" Alexei when he was on the brink of death after spells of hemophilia-related complications.

His weak physique made him unable to leave out of the castle. Diva, masquerading as Princess Anastasia, wanted him as playmate and he always ended up hurting himself while trying to copy her actions. Once Diva severely injured (broke the limbs) of Alexei and after losing her interest on Grigory, she thought of making Alexei her new chevalier. With Diva's blood power and chiropteran body, Alexei felt like getting new life. He thanked her and promised to protect her by killing Saya. However, Saya killed him as Diva got away with Amshel.