How and when Yuan Xi is born is not detailed in the "once-upon-a-time" story Zhenie (Ai-Ai delas Alas) is narrating to Jade (Mutya Orquia).
The pilot episode of My Binondo Girl immediately answered my question. I knew the "one-upon-a-time" story is just made up. Yuan is Zhenie's second born, who died on his birth. And he's the reason why Jade wants to be a boy.
