First you need to have two GBA's and 2 FireRed games. Then using the first FireRed pick your starter and trade it to the other game, but before you trade it you need to pick another starter but different from the one that you chose earlier.(and also capture another pokemon in both games) Then after trading the first starter to the other game, new game the game that has no starter(because you traded the starter to the other game, but you still have tswhe one that you captured earlier) then pick the last starter [ for example earlier in the first game you chose bulbasaur and the second game you chose squirtle then you trade squirtle to the other game(but you will trade the other pokemon that you captured earlier in the second game) after that make a new game in the first game and chose charmander and capture another pokemon in both games again then trade the charmander for the other pokemon that you captured earlier in the second game then viola! all 3 starters in one game.( Pls don't leave a comment if its a negative one).