This is a free mod that will in the future support 4 players and allow interactions between all of the 3rd generation pokemon games. Alpha 1 currently allows 2 players to see each other in the game of Firered or Leafgreen. Updates and more information can be found on youtube, patreon or pokecommunity.
Patreon: https://www.patreon.com/user?u=81688818
Youtube: https://www.youtube.com/channel/UCdXg0-BF9FblZ2GTi3u4orQ
Pokecommunity: Soon