2 players

Yes, two people could play online at the same time, both with headsets, and join a party and talk to others, but the two may not be able to hear each other through headsets (because they're on the same console). So both users should be able to hear everyone
else, and everyone else hears both of them, but the two might not be able to hear each other through headsets and would need to rely on hearing each other without microphone/headset.

I hope this helps.

Hello Jonl L! I'm Kris and I'd be happy to help you with your question.

It will depend if the game supports split screen local multiplayer. Not all games support this.

Yes, you and your husband will be able to play together on online multiplayer games with a second Xbox Gold account.

Get yourselves into a party and the in-game lobby so you'll stay together for matchmaking.

Sign in to Xbox LIVE, and then go to Social.

Select Friends, and then Add Friend.

Enter the gamertag of the person you want to send a friend invite to, and select Done.

In addition to using the on-screen keyboard, you can enter information using a USB keyboard plugged into a controller port or the Xbox 360 Chatpad.

Use the standard message or write your own, then select Send Request.

http://www.minecraftwiki.net/wiki/Xbox_360_Edition

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The game features split-screen functionality,
however an HDTV with a Component or HDMI cable is required for Split-Screen play. Split-screen functionality works with a VGA connection to a PC monitor as well as HDMI-to-DVI cables to a PC monitor. Up to 4 players can play in split
screen*, as well as the possibility to play 8-person online multiplayer game modes in split-screen.

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If you're not using an HDTV with the correct connection you won't get the split screen to work, once you have the display connection set up it should be as simple as pressing start on the second controller to join the current game.