Fire Emblem: Path of Radiance
In the first game, Nasir becomes a double agent in order to save his grandaughter, Ena. He is the one who delivers Ashnard the medallion, and almost throws the world into chaos, but is soon saved by Ike. His love for Ena is everlasting, and here he proves nothing can brake that.
 Fire Emblem: Radiant Dawn
In the second game, Nasir proves to be both loyal to his country, and also an overal better person that what he was in the last game. He doesn't appear until the last several chapters, but he stands strong besides his king, even when knowing that death could be right around the corner. Here he is praised by his king, Dheginsea, for doing so. He even stands against Ena, just to follow his king's orders.
To recruit him, you need to keep him alive and beat the chapter: Endgame(3)