Help!- Who is X??

SPOILER~
The ml can't leave his house because he is technically a test subject. He has been his whole life, at first he grew up in a lab with other kids who have died. He was suppose to be dispose of but red hair guy begged and managed to save ml and give different conditions. But ml still doesnt have many liberties so he cant do much without permission. And Father is apparently ml's real dad and red hair is maybe his half brother. The other test subjects too were his half siblings i think.

Thank you sooo much!