The newborn baby is Yi Yun’s biological child but as mention earlier in the story, FengFeng switched Rourou and bighead which is why Yi Yun has RouRou and since Feng’s aunt has evil intentions, she’s stealing “Feng’s child” who is actually Yi Yun’s child.
Yes Rourou is not Yiyun’s biological son. Their biological mother is unknown because it’s a “surrogate” birth thing where there’s a contract that states the one who’s giving birth to the child will have no relation to the family.
Can sb explain it to me please? Whose child is that? So RouRou isn't yi yun's biological son? Who is the mother of the Bighead and what about RouRou?