Ive heard something maybe possible with retroarch but Im surprised there is no pi zero with an easy multiplayer setup yet ( for instance to play 2 player Mario Tennis on the Gameboy )
In addition, it's very easy to have your rom inside the retroarch folder, then send the whole folder to another person / computer. That way there is no confusion about rom versions, in addition you can pre-configure the controls if the person you're sending the folder to isn't as tech savy.
You can add a small delay to the host to even things out but to properly account for latency is a major reverse engineering project which afaik off the top of my head has only been done for super smash bros melee