You should read Kashikomarimashita, Destiny if you haven't already. The Butler x Butler couple defies destiny in a way because it's an Alpha x Beta. There's a sequal manga called Kashikomarimashita, Destiny - Answer (although in this website it's listed as Chapter 7) that focuses on that couple and the ending turns out great in the end but there's twists and turns to the story.
I'm not sure how kusabi keri makes omegaverse work in kuruboku, but there doesng seem to be any fated pair stuff going on here. however, in the prequel, takaba believed in fated pairs (from the prequel), and although miyabi's physical reaction wasn't strong, he couldnt suppress his heat that one time when he was in the car with takaba. also, takaba once pointes out that miyabi's scent got strong. not to mention, tobinaga also noticed the change in miyabi's scent and he somehow knew that takaba was the cause of it. i dont know if all of these are already fated from the start, or it's because of miyabi's growing interest towards takaba.
if all of these are because they are already fated*
I've alway thougt that omegaverse is so cruel. Especially this fated pair/destiny sh*t, you have absolutely no power to choose who you want to live your life with. What if you are deeply in love with someone, who is really the most awesome person you've ever met, and you feel calm and at ease with them, and want to live this whole fugly life with them and Bumm... an idiot bastar just walz in your life as your "fated pair" ,things happens, he bites you, 'cause that's what an alpha do (i know there are exceptions)
And end up with him for the rest of your miserable life. That's just so cruel it hurts. Not to mention you are driven by some crazy animalistic insticts, what animals actually have better (╯°Д °)╯╧╧