Sure i get this. But no I don't want Kane to be more dominant, I came to this game for the femdom, I only play the dom route for completionist values. I was just wondering why he just seems not to be as brilliant as the rest of his immediate family. Which again kind of feels sketchy to me.
He told the daughter in the intro to test him. That this was his final price. So to say he doesn't care about him, I dont buy that. Alexander fought himself from the bottom to the top. If I remember correctly he always wanted a son but only got daughters. Now he puts the son of the only woman he always loved in an extremly shitty position to see if he can succeed from there, to succeed like he did. I think he would accept Kane to be a slave to one of his daughters, to be just a sperm donor. But I guess that he hopes that it will be different. I think he hopes that Kane could be like him with one if his daughters as his partner, and then together they create the perfect heir to his empire.
If he just wanted Kanes sperm then my god just get it and impregnate one of your daughters with it. There is no need to actually put him through the gambit. Let the daughters fight it out between themselves and be done with it. But no he wanted Kane to have a chance for power.
And if we assume that the daughter from the intro is Olivia: He asks her if she has fooled him too, and she says yes. So this is why actually came up with the idea of Olivia of them both working together from the beginning, basically a gigantic fuck you to the father she fooled from the second they met.
Kane and Olivia were extremly close in their childhood. Maybe, and this is a big maybe, there acutally were in love with each other even before. Maybe Olivia went straight to Kane and told him everyhting. Then tey came up with a plan to fuck with the Karlssons. Maybe the plan was for both to get as much power as they can --> Dom/Dom route. (There also is the sentence about unlimited power in the hand of one person leads to cruelty in the intro. Maybe a good Olivia thought that while this is true, she decided to just change the premise completly and just not fight on her own and was willing to share power with Kane)
Maybe they came to the conclusion that only when Olivia seems to be ruthless and dominates her own "brother" she will be seen as capable enough by her sisters --> Sub route. (This actually would explain the statment from Tess that Kane is ok with everyhting that happens to him, and if Kane is actually into being a sub, this also works

)
To make my tinfoil hat even bigger: We already get sometimes decisions on flashbacks. Maybe all of this only happend in the past when the Oliva and Kane actually are in a relationship. (Basically the actions of the present would shape what happend in the past)
For your argument that they don't talk about it even when they assume they are not under surveillance, they can never be sure that nobody hears everything they say, maybe through the chip or bomb inside of Kane, so they won't risk anything. (I know this is not the strongest argument

, but it could explain it to some degree).
Again I am not at all conviced this is true. I just tried to explain to myself why Kane seems more "normal" compared to his family of super geniuses. And the secret power couple is the best idea I came up with so far.