Yes you can marry for a 10% bonus. Only marry a single character on another account. Can't marry a character on your own account.

• Requires a scroll for the Rings of Mara - (one free with Imperial Edition or purchased from Crown Store for 1000 crowns)
• You and a character from another account must go to an altar of Mara (most starter cities have them as well as 2nd major zone)
• You must be grouped with the other player
• You equip the scroll on a quick slot to use it
• Both of you will be prompted to accept it, and upon completion will each get a Ring of Mara in your inventories. The scroll is consumed on use.
• The rings are inscribed with the other character's name and won't be usable by any other character, even on the same account
• The ring must be equipped to be used to get the 10% xp bonus
• It does use a ring slot and the ring can't be enchanted, so there's a bit of penalty for using it
• The other player must be online and remain grouped with you to get the bonus
• There are several other proximity restrictions that don't seem to be in effect 100% of the time such as; usually need to be in the same zone and same zone instance. Going into an solo instance sometimes stops the effect, but not always.
• There is no game mechanic for divorce (other than removing the rings)
• You can't re-use the rings or get the scroll back to marry another character
• If you want to marry a different character you must obtain another scroll and perform the marriage ritual again

If your computer is capable of running two copies of the game at the same time, you could purchase a second account, and marry a character from it. In my opinion its too annoying worrying about keeping the second account from logging out due to inactivity as well as keeping it in the zone you want. There are some nice "travel to friend" type features to help unlock other zones without questing too much on the second account if you don't want to.