So let me get this straight after Sonia's death and Lara's disappearness Kai a Takao got together?
If thats the case how did Yury and Dani react to it?
If you think that sounds VERY sus my 14 yo ass would reply that "YES I WANTED THE YAOI OLD MEN!!11!"
And then my 24-year-old self would add, "Yeah, but I'll add some cool reasons here and there to make it more believable."
Finally, my 28-year-old self would say, "Here's 34532 pages on why, how, and when. Everything fits, everything works."
I have one rule in my stories: don't change too much. So I had to rework everything around these two dying/disappearing and Takao and Kai getting together, and somehow, I found a good equilibrium.
They don't get together immediately after they are alone. It takes YEARS for Takao because of everything going on and as for Kai... it takes less, but more courage to let go of the past.
I wrote this fic here, in which Takao reveals to Yury that he and Kai are dating. You can see his reaction there.
As you can read, it was a difficult time for Takao, and he found new comfort in someone he somehow forgot he had feelings for. So, a new one took their place.
As for Dani... I think he wouldn't care too. As long as Kai is happy and stable, he's fine with whatever decision he takes.
Besides... being Yury's step-brother?? HECK YEAH!!! The two love to stay with each other!
They would talk between the two of them about the whole ordeal, but in the end, they always go back to the same result: they are happy their dads found happiness.
And it was about damn fucking time they got together, let's be real!