Responses
No I believe the mother when she says their father is one and the same... she is that desperate to keep the man's love （￣へ￣）
I thought she was being kept away from the father? That's why Kiel didn't think his mother was impregnated by his father when he found out she was pregnant?
So Master/Kiel is Rood's elder half-brother. I'm doubting they have same father.
The Uncle sold Rood to the Tower for their experiments. Rood most likely made it through the gate and came back but he was changed. He lost his memories. Which means he did better than the others who returned insane. Maybe he made a deal with the Demon King to return? Which is why Rood's Awake form of the Black Magician looks like the Demon King?