It’s a smart thing to do. If he took a second wife, her family will be involved and they will want second son to be on the throne. It’s basically painting a target on Richard’s back and the Emperor loves him in part that Richard was born from the woman he loved. Makes me wonder how the late Empress was and how courting between her and the Emperor went down.
I also think a tiny bit of reason is that he's the same as Richard, with sub tendencies in bed, since kinks are hereditary...(Yeah I got to know that against my will) So maybe there's also a chance that he also had dom wife. And when she died, the sub didn't look for new dom. It's rare in those times no? Dom women.
Yo a king who never took another wife and didn't have another kid for the sake of his son?! I'm used to trash ass kings in these comics, this man is a real one