Akan Kings of whatever rank have other noblemen who serve them as sub-chiefs. These sub-chiefs do not have hereditary titles and therefore do not have black stools. Besides, each King has a female co-ruler known as the Queen-mother. The Queen-mother is more like a figurehead representing the King's or Emperor's eldest sister and hence the mother of the next King or Emperor, she could rule as a King if she wishes (e.g. queen-mothers mainly from the House of Asona clan: Nana Abena Boaa who ruled Offinso 1610–1640, Nana Afia Dokuaa who ruled Akyem Abuakwa 1817–1835, and Nana Yaa Asantewaa who ruled Edweso 1896–1900). They present the candidate for consideration as King. An assistant king does not have a Queen-mother as his title is not hereditary.