So if I understand the context, “João Gilberto” is a compound (given) name, like “Juan Carlos” or “Bobby Joe”. However, it seems like the family of João Gilberto is treating Gilberto as a family name. English-language media seems to treat it as such; the New York Times, for example, refers to Bebel Gilberto as “Ms. Gilberto”. But I would guess MB gives more weight to Portuguese usage in this case.
I understand that it’s a quite common error of international media treating it as a last name, specially for João Gilberto, but it is a single first name.
For Isabel (the person in question), it’s quite different, since it could be considered a middle name, even not been a family’s name. That’s why I’ve asked.
You are Brazilian?
And you’ve looked at the artist’s webpage and material on Releases?
And no other Brazilian is contradicting you?
I see you as our expert on Brazilian naming practices.
If I understand you correctly “Bebel Gilberto” is a single name, like “Betty-Jo”.
And that the sort name is not “Gilberto, Bebel”, in a way that parallels “Jo, Betty” not being the sort-name of Betty-Jo.
And further a confusion has arisen because “Bebel Gilberto” is sometimes shortened to “Bebel”. But that shortening should be understood as being like the shortening of Betty-Jo to Betty.