I kinda found that weird too, maybe there isn't any special meaning in it, maybe it's for us to be able to differenciate Doyun and Dojun ٩(๑❛ᴗ❛๑)۶
I don't think he was adopted, he looks so much like Doyun that they could be twins (▰˘◡˘▰)
Someone can look more like their grand parents (other relatives) than their parents (dominant genes, recessive genes), genetics works that way. I think it's something like that in dojuns case.
The author said that it wasn’t because of a particular reason, she just made it like that (until now)
Thanks for the clarification
Is it me ? Or in the family photo only Dojun has different hair color and physics comparing to his dad and brothers . It’s like he is adopted or something!
I kind of was so sorry for Dojun in this chapter (37)
http://www.mangago.zone/read-manga/love_shuttle/uu/ibx_chapter-37/pg-1/