[Fontconfig] Is it possible to prevent a font from being listed but allow being matched?

[Zhe Su]

Hi,
  I'm testing three fonts, two of them are supplementary fonts for the
other one. eg. Font A, Font A-S1, Font A-S2.
  These three fonts should be used together. So I add some code into
fonts.conf to prepend family Font A-S1 and Font A-S2 if Font A is
selected. However I don't want Font A-S1 and Font A-S2 be shown in
font list, otherwise user may be confused by these three fonts.
  The reason to split such font into three, is that there are too many
glyphs in this font which can not be put into one ttf file.

Regards
James Su