The only news is that Maat knew, but Osiris and Seth having a past that Seth's forgotten has been hinted at since season 1:
_chapter 41: We are shown Osiris is obsessed with the fear of "being forgotten" by Seth.
_Chapter 48: When Osiris mistakenly believes Seth's dead, he calls out "God of Creation (...) why have you once again taken from me what's mine??" He's obviously talking about Seth.
_chapter 49: Osiris says he's angry at Seth's "unapologetic and ever fleeting spirit", and that single-image flashback of "bald Osiris" hints at a past from before Osiris had his headpiece.
-chapter 144: Horus said that he read in Seth's subconscious (when he met Seth as a kid) about Seth being unconsciously aware of some past from before he became a god, that he (Seth) is on some level is aware of having forgotten all about (ever since the day he, Seth, awoke as a god)
-If we put this all together, what we get is exactly that: that Osiris and "pre-god" Seth have a past that only Osiris remembers, and that's the reason why when Osiris thought Seth had died, he mumbled that accusation, in chap 48, about the Creation god "having taken twice what was his (Seth, who Osiris sees as his 'belonging')".
Oooh thanks sm for this
I'm so fucking dumb I have no idea what matt was explaining to Seth. Like what do you mean Osiris was trying to find his memory. What do you mean they were in love bruh. I'm so dumb