Shine Son:
I think Yoon Jae and Hae Jun will get married first, since they have less obstacles to face compared to the other couples: Hyun Jae with the dilemma of his dad being the adoptive brother of Mi Rae's mom; and Soo Jae with the financial and conning issues, besides he and Yu Na being too young to get married.
The struggle YJ and HJ might go through is concerning having a child. If they are to conceive in the normal approach, their might be difficulties due to their age. They might try conceiving in other ways, and adoption is also a possibility.
Anyway, I just want a happy ending for all three couples, especially my favorite JaeHae Couple. ?
Not only they have less obstacles, I think once YJ is sure of his feelings he won't waste much time. It will depend on how they handle that lie to the tv producer.
Tbh, I want at least one of the couples to marry at least by ep 30, it'd be interesting to see how the family dynamic changes.