Kinji is Kinichi's sibling who he loves very much. He cares for him even though he left Kinji with a lot of trouble after his sudden leave of absence from his life. To Kinji, Kinichi was like a god who he could always trust and was his only family that raised him after their parents passed away before Kinzou and Kaname were known to exist. However, after the events of Volume 4, they have been on bad terms. Even so after all that has happened and even having to fight sometimes, they still love each other as siblings and will try to help Kinji (even if it is indirectly). Also its been said many times to Kinji's disbelief that Kinji has a power that one day will surpass Kinichi's own.
Kinzou Tohyama (GIII) is Kinichi younger genetic half-brother. In Volume 11, it is revealed they have some kind of understanding with each other.
Kaname is Kinichi younger genetic half-sister, who he helped heal after Kinzou (GIII) attacked her and left her in a near death state.