Former Emir of Kano Sanusi Lamido Married His first cousin, Princess Sadiya Bayero as first wife. His wife is the sister of the present Emir of Kano who took over from him.
They started dating when they were quite young. Check out a picture of them about 30 years ago while they were still dating. They have been married for 26 years.
This is Fulani culture.
The richest man in Africa Dangote married from his family and it is expected that at least one of the men who will marry one of his daughters must come from the family to enable the wealth circulate among them.