Look up half-identical twins, or polar twins. Maybe that's where author got the idea from?I really don't like this twin trope. Fraternal twins and identical twins are completely different things. They teach you that in freaking middle school.
Author can always double down on just drawing another identical scene, but this time with it actually being Azuki. I'd take a solid bet on this happening.Hm, so the 'actually a sibling' explanation was correct.
Really, I think the author was a little too blatant with this one. The brother had protruding breasts when viewed from the side in the previous chapter, more than I think is really believable, so I don't think that character was actually drawn as a boy. They 'sold' the fakeout a little too strongly.