Larry Smith wrote on Wed, Nov 30, 2005 08:27 PM UTC:
If you're talking about the Mad Queen variant, the one advocated by FIDE,
your brother is correct. You can have as many Queens as you are able to
obtain. Of course, the promoting Pawn must be on the last rank, not just
the other side of the field.
You can used a captured Rook to represent the new Queen by inverting it.
Or by placing a marker on the promoted Pawn.