Responses
Hiro was adopted since he was baby (as shown in the ch1).
They didnt know the mother but from my understanding, she left baby hiro at the orphanage along with her notes. (Then myb the staff keep it as a keepsake for Hiro if he ever ask for his biological mother/parent to his adoptive parent)
Ahhhhhh ok thank you
Wait so who's him mum? I thought he was a kid they adopted so I didn't think they'd know the mum