From what I understood, it's kinda the opposite tho. He thought he was in love with the brother bc that was the closest person to his real soulmate. If his suddenly developing feelings for Han gyul I'm theorising it's because the link with blondie is getting weaker.
This is actually correct. It was implied by the shaman. Op's "the second u found out he was your ex soulmate" wdym? He knew about it for a long time now (way before Han gyul & Eunhan reunited).
I'm also thinking since his thread is cut-off, he's not bound by fate at the moment, and has more freedom to choose unlike Han gyul whose feelings are heavily influenced by his connection with Eunhan. ٩(๑❛ᴗ❛๑)۶
NO BUT LIKE i like the black haired dude BUT u literally moved from the brother to him the second u found out he was your ex soulmate like idk ab that kinda pisses me off like mc’s the second choice