Board Thread:Lore Discussion/@comment-11549959-20131023234308/@comment-24081142-20131024001957

Correct, the majority of Dunmer are not connected to any particular House, except in as far as they may live in that House's territory and thereby owe them some level of fealty. The Great Houses are Hlaalu (great merchants and friends of the Empire, currently extremely unpopular!), Redoran (renowned warriors), Telvanni (governed by powerful wizards), Indoril (I believe descendants of Nerevar), Dres (slavers and generally nasty bastards, as I recall), and the mysterious Sixth House (I only just started playing Morrowind again after about 8 years, but if I remember rightly this is House Dagoth?)

Some sources refer to seven Great Houses, citing the Dwemer as the seventh before they broke completely with the Chimer.