Responses
Zheng Yan, the black-haired twin, is being experimented on.
The twin's little brother is the one who is missing. (Their mother brought their little brother with her when she came to S1... he ran off and this will cause a ruckus in the subsequent chapters)
Hope this helps~
Kinda confused. Is the little bother missing? Or black haired seme? And why does the dad have to look so much like mc? There better be a reason