The key is that the alpha is one of those manipulative fboys that if you're friend was dating youd ask the friend to leave him asap. So marriage is just a loveless trap. A pretty bird in a cage is not living.
He found out Noah has a kid by him (suspected to be) when SiYeon got sick and Noah had to find treatment for him. Which was about a year+ ago. And he didn't do the paternity test until they met again. So h didn't know about the child, even if he suspects that Noah had been mated with him. Initially thought he had run away as well, but turns out he just had to return to Korea anyways, as his student Visa had expired. Decided to keep the baby, but didn't seem to be on the run. Most likely Ian stepped in bcz Noah was doing worse and worse w/ overworking to pay bills & baby wasn't getting better and suffering from strong side effects. Ian said he waited for Noah to come to him for help but he never did. So, whatever other motives he has is just on top of those I provided.
The plot is
Noah is a goody two shoes
Ian is a playboy jerk
Noah was in love with Ian
Ian was just playing
Noah gets preggo and has baby
Ian AFTER 5 years finds Noah an proposes
Noah gets angy af
What?!?!?!? Why?!?!?
I doesn't make any sense! He loved him, want to be near him, for some reason runs away for 5 yeras, his kid is very ill but because he doesn't want to see Ian, he doesn't take better care of his son, that somehow, it's his reason to live... The alpha is a jerk but here he is trying to be a parent or something, AFTER 5 years... idk