... when he and Masato move together: 17
... when Souichirou moves in: 22
School life: He entered high school when he was 17 (2 years later than ordinary students).
Kaname is the second eldest brother and he is very close to Masato (eldest brother). They both live in the house of their father Kaoru who died. Kaoru's inheritance is to give this house to the person who stays there for one month. Souichirou (youngest brother, high school student, actor and son of Kaoru & his ex-wife) who lived (with his mother) 8 years ago in this house joins this competition.
Kaname's past till chapter 10: