Sadly the way the author talked about the "third couple" in the creators notes before season 3 started and how at the beginning of each chapter of season 3 the author tends to draw requests of the "third couple" in a very couple type way, I have my doubts. Sadly they will probably be a couple at some point and I hate that.
I agree with you but I was also disappointed so many times in the past by other authors that I thought would never go a certain route with a side couple that...I don't know, frankly. I love your analysis and I really hope this 3rd couple stays one sided (and that Owen doesn't get s*xually ass*aulted anymore by Durant).
Also, I want to add that, for Kenny's plan to work, aka putting Rahaman on the throne, getting revenge on what happened to Albin's family and restoring his own family as the true rulers of the North), Durant and Owen have to be removed from the palace. Not killed, but they are clearly Kenny's and Rahaman's antagonists (Owen more than Durant, since Rahaman's parents death is all on him).
So this 3rd couple is very unlikely will become neither lovey dovey nor have a happy ending, because they are basically what's in the way of the whole premise of An Abyss to be actualised.

Honest to God, I don't think the third "couple" is going to be the same as the first two in the way the other two are. I am pretty sure everyone has already come up with this conclusion but some people still think that the third couple are going to end up together and I just don't think that is the case.
The first 2 are supposed to be seen as more consenting since they both go through a slow burn phase where all 4 ( the first couple and second couple) of them didn't know what the other felt and there were so many misunderstandings. I know the Alvin and Kenny situation is fucking weird because he still has the mentality of a child but ultimately, Kenny was trying to be considerate of Alvin (Yes, I know its weird because Alvin would try to throw himself at Kenny as a way to be useful) and trying not take advantage of him for the most part. When it comes to Yexing and raham (sorry, I kinda forgot his name), they went through so much misunderstanding but they cared about each other and didn't seek each other out until they both knew the other wanted them.
Both couples were for the most part consenting and mutual in their love for each other (yes, both their situations are weird AF and are problematic, BUT its fictional so we try not to think too hard about it.
HOWEVER, the third coupling with Owen and Durant is completely different altogether. It isn't mutual at all and it's far from loving. Owen RAISED Durant. He doesn't see Durant the way Durant sees Owen AT ALL.
In fact, Owen is DISGUSTED at the thought of being with Durant like that. It is also VERY HEAILY IMPLIED that Owen was raped by his step father and is traumatized. He is repulsed by the very thought of being with a man let alone the nephew he raised.
This love is very one sided with Durant coming across as unstable and being unable to rein in desires for Owen. Durant thinks what he is doing is nothing more than sweet, courting to the one he loves and either doesn't realize or doesn't care that he's triggering Owen and making him VERY uncomfortable. This couple isn't a couple at all. I can already tell that they WON'T end up together and if they do, it won't be a loving, mutual relationship that we have seen so far. This coupling is meant to be way darker and in no way sweet and caring as the 2 couples we've seen beforehand.
I can feel that this is "coupling" will end in nothing but tragedy. There is no way in hell this has a happy ending.
Anyway, I just wanted to give my two cents. ╮( ̄▽ ̄)╭