This topic may contain spoiler
Pure speculation, but I bet he's the dragon blood duke's bastard son, as his mother was an unmarried woman. And he and his mom got cast out of the family either to "protect" them or because the duke didn't want to have anything to do with a bastard son. That's usually how these backgrounds go, at least.
Since the man behind the voice in his mind kinda looks like an ancestor of the family, Vlad probably got him through that bloodline somehow. So this is probably a "bastard son was cast out but turns out to be the reincarnation of the ancestor" type story.
This topic may contain spoiler
Ugh nevermind. Someone pointed to chapter 78 for his blood line. The current head of the Dragulia family used to "spread his seed" all across the continent. He reasons that some seeds will eventually "bloom". Vlad is one of the results. And it's alluded to that the bloodline runs strong in him as he also has blond hair and blue eyes. But that he has yet to awaken as a full member of the Dragulia family.
I need to reread this cause vlad's background to me is quite hazy all i know is that this dragon captain is blood related to vlad (〜￣△￣)〜