yupppp,
spoiler:
the brother isn't obsessed with him as much in the modern day/reincarnation, orrrrrrrrr the author just hasn't made the move yet (might be a future conflict before the end of this story) bc we are in the earlier chapters of season 3 (raws) and it looks Taehyuk got his memories back and even his past life's memories too but it's still toooo early to end the season all happy-go-lucky. So my guess the author might write modern day Taehyuk's brother's obsession for more conflict and he might use himself/hurt himself to break them up. But that's just my guess, no indication from the raws but with how the brother was impmied to be like in season 1, I might be completely wrong. Bc he did mentioned not caring what Taehyuk does as long as he wants to do it on his own/ it's his decision.
What's with the random stalker arc. I've come back after skipping the backstory loll did not expect a stalker