To add conflict so Ainz could lecture them? I remember you did something similar with Albedo's child which immediately made her stand out from the rest, could also give Ainz the opportunity to show his children the meaning of compassion, which is a trait not many in the Tomb share (not saying they would all be sold on the idea, but it would give them something to think about). And finally, it could do something for Ainz. Could make him more humble and remember his roots, from the way I see his recent interactions, he is slowly being corrupted by the power (Leading Nazarik) he's been forced to wield. I doubt he would even remember that he was human at one point if not for the fact that he's been transmuting to his human body to satisfy his harem.