
I beg to differ. First concubine is wise yes but as she gave up the position of the legal wife it seems she will have a strong attachment that she has the first born so it should be the heir. Also wise women turns at times a 360° change if they see the indifferent or lukewarm husband has a change of heart and starts having affection to another concubine or his soon to be legal wife. It's not to far fetch since the Dad is almost the same as Kangjin but fell hard for his mom.

As far as the manhwa goes first wed was a top courtesan before and was made to be a concubine due to her status and is now about give birth in a few chapters. Next is the sister of the MC best friend which is to be main wife as soon as they are wed. I really feel the the first concubine no matter how wise will be toxic just because she did not get the main wife position so she will use the child for something or be the heir of MC. She keeps saying it must be a boy. What else would a boy be of use in that era other than be the next patriarch after his father. I feel she doesn't bear the child out of pure emotion but instead for a scheme.
It's sad cuz she was supposed to be wise and a great support for the MC. Instead it might be misused
I'm looking forward to see who gonna be the mom of his lunatic son... I don't think it'll be the first wife... But the first wife seems wise just like the son so possibly