You can find the answer to your question in the article "Manuel Vázquez Montalbán y Paco Ignacio Taibo II: hacia un mapa de correspondencias literarias y transatlánticas" by Sergio García García:
Carvalho cuenta con José Plegamans Betriu, Biscúter, su ayudante; Francisco Melgar, Bromuro, el limpiabotas confidente, y [...]. Asimismo, ambos mantienen una relación intermitente y finalmente fracasada con dos mujeres, con un papel muy destacable en sendas familias: Rosario García López, Charo, e [...].
Another possible source is the document Manuel Vázquez Montalbán. Guías didácticas y de lectura para ESO y Bachillerato published by the Institut de Ciències de l'Educació de l'Universitat de Barcelona:
2.4.1 Personajes habituales de la serie Carvalho
– [...].
– Biscúter (Josep Plegamans Betriu): [...].
– Charo (Rosario García López): [...].
– Bromuro (Francisco Melgar): [...].
That is, Charo is Rosario García López, Biscuter is José Plegamans Betriu and Bromide the shoeshine is Francisco Melgar.
The name of Charo appears written in the manager's diary in the novel La soledad del mánager, as we can see in the following dialogue:
–Jaumá nos lo dejó todo muy fácil. En las páginas de su agenda figuran su nombre, tres direcciones posibles y el aviso a una de sus secretarias de que se pusiera en contacto con usted urgentemente.
–¿Tres direcciones?
–Ésta, la de un despacho que tiene usted en las Ramblas y la de su amiga: Rosario García López alias Charo.
My translation:
–Jaumá made everything very easy for us. On the pages of his diary appear his name, three possible addresses, and a note to one of his secretaries instructing her to get in touch with you urgently.
–Three addresses?
–This one, the one for an office you have on the Ramblas, and that of your friend: Rosario García López, alias Charo.
By contrast, as we can see in this doctoral thesis, those of Biscuter and Bromide do not appear in that novel; instead, we will have to wait for books published later in order to learn about them.
That of Bromide is found in the novel La rosa de Alejandría, in this dialogue between Carvalho and Bromide, where we can see that, up to that moment, Carvalho ignores Bromide's real name:
–Ahora te escucho, macho. Ésa es una pregunta de los viejos tiempos. Así se iba a las cosas. Y puede que te sea útil, porque aún conservo mis contactos, y para algunas personas, muy pocas, el caballero legionario Francisco Melgar sigue siendo el caballero legionario Francisco Melgar.
–¿Y quién es ése?
–Yo.
–No sabía que te habías cambiado de nombre.
–¿Tú te crees que yo nací llamándome Bromuro? ¿Tú te crees que mi padre y mi abuelo ya se llamaban Bromuro? ¿Tú te estás quedando conmigo, Pepe? Venga el número ese.
My translation:
–Now I’m listening to you, man. That's a question from the old days. That's how things used to be done. And it may be useful to you, because I still keep my contacts, and for some people, very few, the legionary knight Francisco Melgar is still the legionary knight Francisco Melgar.
–And who is that?
–Me.
–I didn't know you had changed your name.
–Do you think I was born being called Bromide? Do you think my father and my grandfather were already called Bromide? Are you pulling my leg, Pepe? Hand over that number.
That of Biscuter appears in the story "Desde los tejados", published in Historias de padres e hijos, in this dialogue between Carvalho and Biscuter, where, in the same way, we see that Carvalho was unaware of it:
–Si te mueres antes, yo te pongo una necrológica, Biscuter.
–¿Y qué pondría, jefe?
–Lo mío no es la literatura, Biscuter.
–Haga un esfuerzo, jefe.
–Ha fallecido Biscuter...
–Me llamo José Plegamans Betriu.
O sea que Biscuter no se llamaba Biscuter.
–Pues bien: ha fallecido José Plegamans Betriu, más conocido por Biscuter, destacado profesional de la investigación criminalista... o no, mejor dejarlo en criminalista...
My translation:
–If you die first, I'll put an obituary in for you, Biscuter.
–And what would it say, boss?
–Literature isn't my thing, Biscuter.
–Make an effort, boss.
–Biscuter has died...
–My name is José Plegamans Betriu.
So Biscuter wasn't called Biscuter.
–Very well then: José Plegamans Betriu has died, better known as Biscuter, a distinguished professional of criminal investigation… or no, better leave it at criminal investigator…
