This might be a bit trickier than it initially sounds. You can marry both AI characters and real people, but both require convincing. The stakes are especially high for real people, whom you can propose to after inviting them to your game through Xbox Live. That's because if you do decide to get married, all of the wealth you have accumulated through the game is pooled into one shared bank account. And if you wind up getting divorced, that money is split down the middle. Once you get rich in Fable III, you'll have to seriously weigh the pros and cons of marriage before jumping into bed with a friend.
Marriage, if played properly, can be a very lucrative opportunity for an enterprising player. You can always get divorced and re-marry another player on Xbox Live. You can even marry multiple partners at once, with each getting their own house to share with you. Of course, if you end up on the flip side and marry poor, you could find all of your hard work go up in smoke. The wedding is going to cost money. The kids could end up costing you more (they stay with the host in the event of a divorce). It's a lot of responsibility just for the option of sharing a bed and getting busy.
As Molyneux put it, "Don't invite poor people in, it's just a tale of woe."
Now, it might be a bit awkward tossing out marriage proposals to all of your friends on Xbox Live. That's why Lionhead included the option of creating business partnerships. These carry all of the same benefits -- and risks -- of marriage without the bits that happen after the lights go out.
Co-op play in Fable III isn't all about money, of course. The demo I saw also touched on combat, giving gifts, and world changing events. That last bit was quite interesting to see in action. The world of Fable III will literally transform depending upon how you play it. Noble folks will find the land of Albion filled with glistening with fresh water and blooming flowers. Others bent on industry and wealth will find the same lakes and meadows turned to muddy mines without a bright color to be found. It's an idea that has been touched upon in Fable since the very first entry into the series, and now it seems that those promises are finally being fulfilled.
The differences in how the same scene can look are astounding, and you're free to see them all without replaying the game. Simply join a friend's game and you can see how their world looks for yourself. Co-op in Fable II was sorely limited, with an annoying camera and no option of bringing your own character into other worlds. That has all been fixed for Fable III, even going as far as letting you take your pet dog into another person's game.
I haven't yet had much of a chance to play Fable III, but what I've seen makes it look far better than its predecessor. The design feels much more cohesive and focused, and the visuals look spot on. I just hope it plays as well as it demos, because if it does this could be one of the best games left to come out in 2010. We'll know for sure in October when it hits store shelves.