The AIONIAN Brotherhood was founded in 1930 by the principals of:

Abeokuta Grammar School (founded in July 1908), Late Rev. W. R. B. Kuye
Ijebu-Ode Grammar School (founded in Jan., 1913), Late Rev. I. O. Ransome-Kuti.
Ibadan Grammar School (founded in March 1913), Late Rev. A. B. Akinyele.
Ondo Boy's High School, Ondo (founded in Jan., 1919), Late Rev. Canon M. C. Adeyemi who first suggested the idea of the Brotherhood at a meeting held at St. Andrew's College Oyo.
The four schools are the foundation members of the Brotherhood, and the name "AIONIAN" was derived from initials of the four schools, "AIONI", with the last "AN" added to make it adjectival. Other members joined later at different periods. By 1955, membership of the AIONIAN brotherhood had grown to twelve, all in the former Western State of Nigeria. With the creation of Oyo, Ondo and Ogun states in 1976, the schools were coincidentally divided into three equal parts with four in each state. The names of the schools and the year they joined are: