Responses
It still is that, kinda, or rather how it started. His sister wasn't under his control, she just fell for someone who didn't have a title. The obsession came from grief of that loss. The one he obsessed over also left and died during childbirth, so he's blaming a family from "taking her." in his eyes, as soon as they are out of sight, they perish forever.
I was wrong about former emperor being so protective… it was about control and obsessed