Yk what my theory is?

The 2nd brother (black haired) has a thing for the older brother (light haired) and vise versa.

The 2nd bro doesn't realize that the feelings he has for his older bro are not platonic but the older one knows for sure that he loves his younger brother (2nd bro).

Oldest and youngest (red haired) were abused the monster- I mean father and have hidden it quite well from the 2nd brother. I wonder what his reaction will be when he finds out. He loves and respects that monster- I mean his father.

Also, this is a story of abuse why does everyone keep calling it incest??
The brothers did not willingly get abused by that mons- the father.

If you're calling it incest based on the feelings between the brothers then okay sure it's incest but do not call it that based on the relationship between the father and his adoptive sons that's abuse.

Also the reason I think 2nd bro hates the youngest is probably cause he's jealous that the oldest is good to him (infront of the 2nd bro at least) and oldest is fucked in the head tbh he should've protected the youngest like he did the 2nd bro but who am I to say what's wrong and what's right, never been in his shoes, idk how he must've felt. He was terrified of the father that's for sure.
Okay babye~