This is the pathfinder wiki which has lots of back stories and all the information on like Gods, creatures, and their background in the pathfinder world including that of different planes.
http://www.pathfinderwiki.com/wiki/Pathfinder_WikiHowever the direct information related to Brevoy is located here with links to data that hasn't yet been updated as well as info on the royal houses.
http://www.pathfinderwiki.com/wiki/BrevoyI've checked them over and none of the information on page has anything spoiler worthy. Though it is a bit bare at the moment.
I should also mention you are allowed leeway in making your backround as long as it's not too out there or out of control. For example House Garess which you guys used according to the wiki already had an heir that is a dwarf, but having you guys do your thing with the four brothers I have no problem with.
