*By far, most three-stage evolution families were introduced in Generation I, with 27 such families having their roots there (though not necessarily their most unevolved or most evolved forms). Because of branch evolution, 29 of the second-evolution Pokémon can count themselves as members of a Generation I evolution family. Generation V has the second most, with 19 three-stage families (none due to branching). Generation III has the next most, with 16 three-stage families that end in 18 Pokémon (again due to branching), while Generation II and Generation IV have the least, with only nine and six families, respectively, that end in a third member.
**Generation V, however, has introduced the most original three-stage evolutions, as many of the three stage-evolutions stemming from Generation I include Pokémon not introduced in the same generation as their evolutionary relatives.