Yeah but he doesn't talk about his childhood too much except for just his sister. So what if she was somebody that was local and he got her confused because she's the only one that he can really remember so he just naturally remembers her as his sister. I know it's a long shot but I'm kind of hoping LOL and I know it sounds crazy but it would be so cool. And it would explain why Jeha was so attached from the very beginning. Yeah because in the main characters end it could just be Memory wipe you know like when people get in an accident and they only remember fragments of their memory so they piece it together to make a whole memory and sometimes that whole memory is false.
Okay okay hear me out I'm probably going crazy. What if the main character is the "dead" son. Because look at their eyes and just a fluffiness of their hair they look a hell of a like.