2 players with one keyboard? One left handed mouse and one right handed?
2 players on one keyboard is already overcrowding.
From the old games i used to play when i was kid, i remember if there was 2 players, it was often one player on the keyboard and the other with the mouse... With simple games that needs only 2 keys of course. No wheel mouse etc in these times
Nowadays you can play with wireless console controlers which is far simpler than 2 mouses. Even big studios have not tryed it for 2 players.