SPOILERS

Its a possibility but not confirmed. It might go that route but there are other cryptic hints that give us different leads.. for example messages like , " His brother always followed him" "Brother copied his words and actions, He was annoyed with his brother. And before he knew it he thought he was lovely. He taught his brother knowledge. He denied his feelings They should not break the taboo until they became gods"

This message could be abt their past life selves where osiris couldve had younger brother seth tag behind him. He taught seth and developed a one sided obsession with him

Or it could also be about seth and past life horus who followed him everywhere until seth started feeling affectionate towards him and they grew closer not necessarily as lovers but maybe as siblings but osiris in his obsession fcked shit up? (Og myth horus is actually 5th n youngest ennead sibling. Egyptians called him Horus the Elder and we've been hinted abt his existence in the manhwa as well ) so Both theories atp are possible but i hope its horuseth past lovers not osirishit lol

SPOILERSS are you talking about where we find out that there was a god that looked like Horus/one that passed their power to him?

It most likely IS horus and not a god who passed their powers. Because u see.. Horus in actual mythology is the 5th n last ennead sibling. The 5 siblings represent 5 days of week n were worshipped as thus in early to middle kingdom egypt. Later integration of greeks n hellenistic propoganda pushed by ruling greek ppl popularized the 4 sibling pair ennead but local citizens still prayed to osiris isis seth neph n horus as children of nut n geb. This version of horus is called Horus the Elder aja Heru-ur/Heru-wer/ Haroeris. In this manhwa his existence has been hinted quite strongly.
1. The infinite cave void where neph talks about it
2. Hieroglyphics murals hidden by mojito in diff chapters translate to cryptic msg abt a forgotten "youngest sibling"
3. Horus intution which Thoth said was stolen goes similar to the cryptic messages hidden abt their past life as demigods.

We'll know this if seth regains his past life memories. High possibility he and horus were supper close if not romantically n osiris had a hand in horus's killing. Isis left to find a way to resurrect her youngest brother n she absorbed him in her bossom n gave birth to him as current horus. If u remember, horus in one chapter says its all thanks to seth that he exists cuz he knows apparently osiris didnt have any plans to have kids wifh isis. Which sounds odd unless he knows HTE could come back