Siegbert

Siegbert is the son of Xander and the cousin of Forrest, as well as one of the two paternal grandsons of Garon. Like the other children of Fates, Siegbert was placed in the Deeprealms to keep him safe from the war. Siegbert became particularly close to his father and would spend his days learning all he could from swordsmanship to penmanship in an attempt to impress his father whenever he would visit. He also would regularly receive news of his father's efforts in the war.

(Source: Fire Emblem Wiki)