This is a spoiler for the kids ending not the parents so they might actually end up together. Since hyeol and kkotsu become siblings they don't end up together and instead fight for jeonghan so it doesn't lead to incest even though they aren't blood related siblings. Atleast that's why I think the author changed kkotsu to alpha instead of omega like he was originally supposed to be.
idk but i too prefer hyeol to kkotsu, since kkotsu kinda became one of those “i bet you’re a tasty omega, and i want to eat you up asap” type of alpha, while hyeol is actually minds jeonghan’s feeling and telling kkotsu to f off and not to things that would make jeonghan uncomfortable. and jeonghan seems to be confused bcs he thought that he always like kkotsu, but hyeol seems to shaken his heart. you’ll never know tho bcs it ended with an open ending lol. wished the author made their own story bcs it’s seems even more interesting than their parents’ storyლ(´ڡ`ლ)
its kinda end with an open ending, jeonghan turns out to be the omega while hyeol and kkotsu are alphas, they made somekind of agreement to respect each other as alpha and omega bcs, i think (sry mtl problem), jeonghan dont want to choose and he doesnt believe that omegas are necessarily need an alpha in their life or smth. but the agreement will only be valid until they turn 20, then its either jeonghan will choose between hyeol and kkotsu or they become a poly couple (yumm)