What do you call your father’s brother’s daughter’s son? What about your mother’s step-sister’s son? Most young people will tell you that the answer is always ‘cousin’, ‘uncle’ or ‘aunt’, depending on their age.
It may be because family dynamics have become increasingly complex, and more families now comprise two different families coming together. Or it could be because the English language has never been able to cope with the multi-layered nature of a true, extended African family.