Andals

From Asoiaf

The Andals invaded Westeros long ago.

House Lannister descends from Andal adventureres who carved out a mighty kingdom in the western hills and valleys.

The Andals swept over the Iron Islands and extinguished the line of King Urron. Many of the island lords intermarries with the conquerers.

The Kings of Mountain and Vale, ancestors of House Arryn was one of the oldest and purest lines of Andal nobility.