Honestly
Jc and wwx being "adoptive brothers" is actually more of a fanon (I don't count CQL as canon really) n being martial bros/sworn bros is very different.
At best they are best friends n comrades. Author herself hasn't called them "brothers" in her interviews +

The decision to see them as more "familial" bros is mainly fan perspective n hence a fanon. Martial family is more like....say in Indian context, a guruji taking in disciples n while said disciples refer to e/o as "bhai, behen" two disciples under the same guruji can get married+

(at least I don't remember there being taboos). What IS weird actually is when a guruji has a romantic relationship with a shishya. Cz guru-shishya relation is seen as sacred. Anyway, deviating from the point here.

I understood Martial sect ties thru my understanding of gurukula

In the Vedic education system, students left their homes to live under the guru n while they are family they are also not. They are STUDENTS n the only brotherhood they share is studying under the same guru (ofc in Mahabharata, the Pandavas n Kauravas were actual blood+

Brothers but that's different)

I think martial Sects are similar except more militant along with the usual education of the 6 arts.

So when jfm took in wwx, he was taking him into the martial family not actual family. Even wwx himself knows the fact when he refers to himself+

As a "guest" or the "son of another" n why he has trouble believing jfm would like him over jc coz he doesn't see himself as an adopted son. No one does actually.
And it's BECAUSE wwx isn't adopted into the family that the fact that jfm favours him over jc is more "scandalous"+

To other ppl coz "jfm favouring one of his STUDENTS over his own son? What??" If wwx had been adopted as a "son" ppl wouldnt talk as much. Nor would they find the fact that wwx was the favoured son so shocking.
Plus, this point has been mentioned b4 but ymj is a big clan+

N if wwx really was an adopted son ppl wouldn't continuously refer to him as "son of a servant". The only adaptation that refered directly to wwx n jc as "bros" is CQL which, in any case, is the faultiest adaptation n apparently from what I know, it was also a translation error+

In the Netflix subs (Netflix subs are crap anyway). In the donghua episode the "they grew up more like brothers than a master n servant" is more to highlight on the fact that jc n wwx grew up as "EQUALS" despite the class difference (at least that's how I understand it)+

I'm not really sure why I'm writing this thread but I'm writing this thread. To satisfy myself ig.

In any case, going thru the novel, once again I've noticed neither wwx nor jc refer to each other as brothers even ONCE, not even as shidi/shixiong so even they don't see e/o+

As bros but as friends or equals. Jyl is the only one who sees wwx as a brother but that's more of her personal feeling (kinda like you have a close friend you KNOW u will never have anything romantic w coz that friend feels more like a sis/bro)+

When jyl answers to Madame jin's concern about her n wwx being seen as something more, she means it more like "u don't have to worry cz a-xian is more like a little bro to me. I am not in love w him"
Jc & wwx's bond is never even CLEARLY mentioned of what kind it is+

N while ofc according to canon w.angxian is the only cp so there's def no romantic relationship between jc n wwx, but in fandom jc/wwx pairing is okay and is NOT inc3st cz they aren't adoptive sibs, they're MARTIAL sibs. Fellow shishyas. N in canon even if they see e/o+

As "we are friends with more bro feels. I ain't dating him" in fandom it shouldn't matter coz it's fandom. And fiction. And we can do what we want.

Once again, I'm not even sure why I wrote this but heh. Yeah. Leaving this here. Ch3ngxian ain't inc3st.