Responses
The Emperor only has one wife, which is the Empress and she is the mother of the three children (2 princes and 1 princess). You could call Estrella’s mom as a concubine and she made a deal with the Emperor to have his child—so, I guess, in this case, you couldn’t really call her his wife... she’s just the mother of his child.

I’m very confused right now, does it mean the emperor had three wives(?)
The prince and the other princess’ mom, then estrella’s mom, and now selina?