Responses
no, their pheromone compatibility already noticeable before eihyun became pregnant (?) I'm guessing, there's a hundred percent that they are a fated pairs (if this also works in their world)
I think it's already stated that they love each other scent even before he got pregnant but after he became more sensitive towards taeju scent
Ooooh their pheromones compliment and help each other... wait, or is this because Euihyun is carrying Taeju's baby?
So, since Euihyun is (presumably still) carrying a tiny Taeju in his belly, Taeju's alpha pheromones can be the one to calm down his emotional instability.
**I remember this from another omegaverse story (Unscented Trajectory). Where once the omega was pregnant with the alpha's baby, no other alpha's pheromones could help calm them down.