well we already have at the least 3 persons, princess, odette and the loli, well probably all of her people there would be part of his faction hahaha.
Don't forget the commerce guild. And any other descendants the author might eventually pull out that may have landed (or maneuvered themselves) into positions of power.
Frankly, from an outside perspective the Yuuki faction is scary:
An ancient conspiracy from a time forgotten to the cruelties of history and war, hailing from an eerie, abandoned village once led by what was perceived to be a demon of some sort. It's members are countless, with powerful actors all over the kingdom, all the way up to the royal palace.
To top it off, their mysterious leader wields a particularly powerful Lord, a weapon considered the pinnacle of the worst war history can remember.