Bloodlines and natural dispositions probably work like this.
The child over a hundred days old can now sit up very well, and when he grows tired of lying down, Yan Heng starts fussing about wanting to be held upright. At first, Your Majesty didn't understand what this meant until Yan Heng himself explained it aside.
Then Your Majesty said, "Indeed, he is our child, so robust at such a young age, full of energy."
Yan Junchu maintained a smile.
The courtiers: ...
Your Majesty actually picked the child up vertically and carried him from his throne into the midst of the courtiers, pointing to each important official of the court so that he could recognize them.
Knowing full well that such a small child wouldn't understand, but seeing his particularly excited face, Your Majesty felt in an exceptionally good mood.