The Einzberns specialize in 'the golden rule of the Rhine', and thus were the best suited to make an imitation of the Holy Grail.
In Fate/stay night, the three families are the Einzbern, Makiri, and Tohsaka.
The creators of the Fuyuki Holy Grail War are: There are two different sets of families for two different Holy Grail Wars. The term Three Founding Families (始まりの御三家, Hajimari no Gosanke ?) refers to the three Magus families who created a Holy Grail War system.
