In Erin-Ijesa, Osun State, in the western region of Nigeria, Kumuyi was born into a Christian family.
He finished his secondary schooling in 1961 at Mayflower School in Ikenne, Ogun State. He then went on to the University of Ibadan, where he earned a first-class honors degree in mathematics in 1967 and was named the school’s top graduate that year. The University of Lagos offered him a post-graduate course in education after that.