All things considered, the Song Family still has too few young women. Right now, it seems there's a shortage; the older ones have already married, while the younger ones are either still nursing or there's only one like Song Ruwei who is half-grown.
Other families at least have some cousin young ladies living in their mansion, who can accompany the adults to banquets.
But the Song Family, the old Madam was a child bride, so there is essentially no maternal family to speak of.
And Madam, her maternal Duke Zhongyong Mansion, she doesn't encourage bringing her niece to live here, fearing that she might harm her own son.
Then there's Mrs. Jiang. Coming from a merchant background, sorry, she's an only daughter. Her father had deep affection for her mother and never remarried. Regarding the continuation of lineage, he had an open view, believing a daughter is also a bloodline continuation, so he didn't mind not having a son.
