The first green sprouts of multiplayer should push up into cutesy farm life RPG Stardew Valley [official site] at the end of this year, publishers Chucklefish have announced. Chucklefish are chipping in with multiplayer and expect it'll be ready to launch properly in "early 2018". For now, they've explained a little more of how it will work.
Chucklefish's Tom Coxon says:
"Shortly after you begin the game, Robin will offer to build up to 3 cabins on your farm. Each cabin will house a farmhand, controlled by one of your friends.
"Farmhands can do almost anything the main player can do. They can farm, mine, fight, fish, forage, marry NPCs and take part in festivals. Each player has their own inventory. When a farmhand is not connected, their inventory can be managed through a chest in their cabin.
"Certain decisions can be made only by the main player: when to sleep, when to start and end festivals, and whether to side with Joja, for instance."
It won't require dedicated servers, and will use Steam invitations (or probably something similar outside stuff) to arrange farm hangouts.
Oh, and yup, multiplayer marriage will be in. "Player-to-player marriage won't use the mermaid pendant, but rather an alternative method that requires a similar amount of effort to wooing an NPC," Chucklefish say. "We're still working out what that will be." Hopeful not a load of chores like with NPCs.
Multiplayer Stardew Valley is already possible through a player-made mod, though it's cruder and certainly jankier.
"There WILL be bugs and crashes. You have been warned," creator 'spacechase0' says. "This is only meant as a temporary solution, until official multiplayer comes out."
Still, if you really want to farm with friends right now, that is already out and does broadly work. Not to mention that it's hugely impressive for a mod.