Plus, his graying hair could once have been Targaryen silver ... Addam is likely Corlys' son as well. That means the Old Valyrian blood of House Velaryon runs in Addam's veins.

After the dragons are gone, their silver hair, temper and the ability to speak High Valyrian are what's left of the Targaryen tradition. Being a Targaryen means royalty and magic in their blood ...