» Sat Jun 09, 2012 7:25 am
Sadly there are a limited group of marriage-able NPCs inspite of what was implied by Bethesda in interviews ='(
However, if you are playing on the PC you might be able to add the NPC to the marriageable group via the console.
elderscrolls.wikia. com/wiki/Marriage
The above link has info on all NPCs that can be married. It also has instructions on "forceing" a NPC into marriage.
Pro Tip: To open console press ~ key which is directly left of the 1 key.