Kageki

is the twin brother of Katazu, the husband of his wife, and the father of his son.

Background
Kageki had loaned money to Shikazo one time and after the birth of his son, he needed the money and asked Shikazo if he can be repaid but he refused. After a small scuffle, Shikazo fell and hit his head on a pickling stone that was hard enough to kill him. Since then, Kageki with his wife and son, went into hiding, while his twin brother, Katazu, took his identity and got the attention of his pursuers.