Dage does have a younger sister, Mirna, who lives in Anghor with her half-dwarven husband, Gregor. Dage was never very close to his sister, who was born well after the founding of West End. His sister and brother-in-law were among the first to move to Anghor after the Dread War.
Dage did travel with his mother and father from Dimhold, though he was only a young dwarfling at the time. From his father he learned a lot of his 'scout' oriented skills- hiding, moving silently, how to spot and listen, wilderness lore/survival, etc. His mother taught him the more mechanical aspects of his skill set- how to deal with locks and traps, using rope, how to use a bullwhip (both as a tool and a weapon), etc. He would have been 22 when he 'graduated' from the scout's guild. As I wrote, his father died in West End during the Dread War. Dage fought both in and around West End and was among those who marched to the city of the Darklings at the end of the war. He began his tenure as an instructor at the scout guild shortly after the founding of the Aidman Institute, which was in 27AF if I'm not mistaken.
His mother does live in West End, and Dage helps to support her and the family home there. He almost never actually sleeps at the Foeender residence, though he does have a room there- his quarters are his office at the scout's guild, and I figured that since most of the young scout trainees stay at the guildhouse he would stay with them to keep an eye on them.