Ok, if he had implanted the spys in her palace and knew it all the bad stuff that she was doing to the twins, so what he could do? Nothing because she had his life in her hands, so he wouldn't risc interviewing bcs he is the Emperor, and he has a lot of enemies. And he had his other sons to protect. And he couldn't even treats her.
And the think with the blonde hair is bcs that is a proof that they are actually his children, bcs he didn't do anything with her, and if they weren't born with the blonde hair, he would think that she lied and tried to fool him.
And the think about that he "Hopped that they were dead" that is in some comments, i disagree, bcs he knows children born between races don't live much, and he naver heard about one of them survive to/after 5, so he was concerned about it and he feared about that happen to them, so when he stopped receiving the things that their mother demanded, his biggest fear come true. I can understand why he didn't go there bcs of his fear to see the dead bodies of his children.
The thing with the twins Guardian, if i'm not wrong, the first one to know about him was the second prince and the first time he saw him was when he first meet the twins. So before the Emperor know about him, was maybe after their mother death, and i do think the second prince didn't tell the Emperor yet because he get to check the twins and when he was going back, at the same time the twins mother died, and he had to heal the Guardian, and late on he knew that his father already knew that the kids were alive. And after healing the Guardian the second prince answer his questions and explaining everything.
I like the fact that he has flows, it show that at the end of the day he is a normal human with flows, that some times make stupid things/decisions
Well this is my opinion 💚💚💚💚💚