Who is Manuelzinho from The Viceroy of Ouidah and what is their importance?

Manuelzinho is the half-breed Brazilian Indian who moves in with Francisco's mother after her husband dies in an accident when Francisco is one year old. Manuelzinho, who earns his living by catching snakes and selling their meat, is a born wanderer who never stays more than a week with Francisco and his mother before he leaves on extended trips.