|Manga||Phase 18 (Posthumously)|
Futaba Yuibishi (結菱 二葉 Yuibishi Futaba) is Kazuha's younger twin brother. He died in a shipwreck in 1957 while eloping.
He is a young adult with a thin physique. In every flashback, he is seen in a formal suit. His appearance is virtually identical to Kazuha at the same age except, perhaps, in how their hair sweep (Futaba's seems to sweep to his right).
Futaba and his brother, Kazuha, were born as twins to unknown parents. The two ran a business together which was going very well in the post-war economy. However, Futaba wanted to give this up so he could be together with a foreign woman he loved. Kazuha fought with him over this.
During an event celebrating the success of the company, an explosion rang out and he declared his desires to be with this woman before shortly departing the event with her.  He would later elope with her, but perish when the boat he was on sunk. Kazuha claimed Futaba's body was his and has since then gone on living in Futaba's identity.  His room in the Rose Mansion is left as it was. 
References and Citations
Yamamoto • Mr. Umeoka • Futaba Yuibishi • Alice (Rozen Maiden (2008))
Kazuki Shibasaki • Matsu Shibasaki • Yuna Kuwata • Hitomi Sakamoto • Enju
Ageha • Yamaguchi • Megu's Father • Megu's Nurse • James • Head Manager