After Shirahime Thorne is resurrected and takes her place as Fifth Division Taicho, she finds and adopts Daichi Takeya.
Shirahime allows others to believe Daichi is only adopted, but he is actually her biological son (via an unknown incarnation).
He is a God/Shinigami hybrid. His father is a shinigami, and a certain person claims he is Daichi’s father. The identity of Daichi’s father is a forbidden topic in Soul Society.
He is the youngest of Shirahime’s children until his zanpakuto, Aoi Raiko, incarnates as Raiko, his younger twin sister.
As of Fifth Division in the Red, he is the third seat of the fifth division.
He appears to be older than Yachiru, but Yachiru is considered the oldest of Shirahime’s children as she comes from Shirahime’s first incarnation, Shirayukihime no Tenjou.
SPOILERS FOR FIFTH DIVISION IN THE RED BELOW:
Daichi and his family consider Yumichika to be his father. Raiko is his actual twin sister that Shirahime hid inside of him so that their biological father (simply known as “the bad man”) did not find out about her. Later on, the family lets others believe Raiko is just a zanpakuto spirit to keep her safe.