Who is Isidoro da Silva from The Viceroy of Ouidah and what is their importance?

Isidoro da Silva is the first-born son of Francisco and his Dahomean wife, Jijibou. He is eventually sent to Brazil to live at the plantation with the Cutinho family, but he becomes so out-of-control with drinking and whoring that Joaquim Cutinho casts him out. Isidoro goes up in France, then returns to Dahomey as a dandified fellow with aspirations to start a palm oil business. Francisco finds Isidoro to be useless, but after Francisco's fortunes decline, Isidoro becomes head of the family.