On Game Of Thrones it’s repeatedly mentioned that the Starks (and the Wildlings) are descendants from the First Men. This is a fact that is said proudly, as if the First Men were the rightful inhabitants of Westeros and thus their claim to the land is stronger than others.
While we now know, thanks to the previous fact, that that isn’t the truth and that the First Men were actually from Essos, there’s actually a darker fact at play in the history of the First Men. They nearly slaughtered an entire race to get what they wanted.
While the Starks and others may be proud of their heritage, that doesn’t change the fact that when the First Men showed up on Westeros they wanted the entire place to themselves. So they mowed down entire forests – destroying the homeland of the Children Of The Forest – and went to war.
Using their weapons made of bronze, their superior technology, strength, and their increasing numbers as they called more over from Essos, the First Men invaded every inch of land they could find and established kingdoms throughout Westeros. The Children tried to fight back with magic, even going so far as to break the land bridge with Essos so no more humans could cross, but the First Men were relentless. The fighting carried on for centuries until a peace treaty was finally signed.