@heimdal
The thing is, the first prince (in age) isn’t always birthed by the legal wife (queen). That is the case with the current crown prince, Gil’s first brother. The first prince’s mother wasn’t the queen at first and Gilbert’s mother had been the queen prior to her passing, so that’s why Gilbert was crown prince originally. It’s normal for the monarch to have many consorts.
When Gilbert’s mother died, the first prince’s mother became queen as she had the most influence out of the concubines and he became the new crown prince.
I don’t understand the raws that well since my Japanese is quite poor so I use a bit of mtl. The crown prince is married but with no child.
I’m reading from chapter 9 of the raws.
In part 9-1 ~ 9-2 the queen (1st prince Jerik’s mother) says rude stuff to Rina and somewhere in there she said something about birthing a baby, and Jerik steps in the ask her to stop.
In chapter 9-3 we see the queen say this: イエリクの側妃にお上がりなさい。 Which translates to “You should go become Jerik’s side consort.” I’m not confident in my Japanese but that specific sentence was very clear. I’m confident about that even without Google.