WARNING!!! SPOILERS AHEAD!!!

TSUKIYONO OMI

Omi has got the most frustrating history i know... At a young age, his name was, in fact Taketori Mamoru. Son of Taketori Reiji. Omi, is actually the result of an affair between his mother and Taketori Shuuichi (Reiji's brother and also Persia). He had two brothers - Taketori Hirofumi and Taketori Masafumi and one sister - Sayaki Ouka... Ouka however, is the result of an affair between her mother and Reiji... So... In fact, Omi and Ouka aren't brother and sister, they're... well... they can be considered cousins.

At one point in time, Mamoru was kidnapped and held for ransom. Reiji refused to pay the ransom and left his son to the kidnappers. Shuuichi rescued Omi from the kidnappers and introduced him to Weiss.

Omi doesn't remember anything about his life before Weiss until a later portion of the series.