It’s hard to say because we don’t get to see inside their heads, but—
Mild spoilers:
in one of the later chapters, (15+) Hayden looks like he’s jealous and also wants to spend more time with Brett outside of his rut periods (it seems like they only really see each other then), and…also in chapter 22, Brett tells Hayden his fave part of the day lately is hanging out with him…that it makes him happy.
So, it’s hard to say who’s fallen (will fall) first.
It feels like they’re both kinda there.
Spoiled
From Hayden pov, it’s obvious Hayden fall first, he secretly annoying and jealous to anyone who interact or skinship with Brett and super against the 3some idea of Brett, but yeah, we not get to see Brett pov yet, maybe Brett did fall first but that very low chance from what happened in ss1…
I hope the uke falls first