The Ozuki family administered the records of Imperial Japanese Council of State from the Middle Ages, and was, due to its inherited position of fifth rank (sadaishi joshu), known as the family of administrative service; when OZUKI no Hirofusa, the son of 小槻長業, and OZUKI no Takamoto, Hirofusa's younger brother, fought over the position, the family was divided into two streams with the position of fifth rank going Takamoto and his descendents (the Mibu family) and the post of sanhakase (a position teaching mathematics and looking after mathematicians) going to Hirofusa and his descendants (the Omiya family).
小槻氏は中世より太政官の諸記録を司り、五位の官務（左大史上首）を世襲したため官務家と呼ばれたが、平安時代末に小槻長業の子の小槻広房と弟の隆職がその職を争い、五位の官務は隆職の子孫（壬生家）、算博士は広房の子孫（大宮家）が世襲することとなり、二流に分裂した。