If Real Madrid had a bigger offer, Khephren Thuram would have a hard time refusing Real Madrid's offer, but if it was almost the same offer as Juventus, I've no doubt that Juventus would get his services.
The factor of his parents closeness to Juventus could be one of the reasons, we can see the same thing with Erling Haaland. Moreover, if Khepren Thuram goes to Real Madrid, I doubt he will be an immediate key player there, he could be loaned out first because he's not yet mature, so I don't think it would be a good move to go to Santiago Barnabeu.
Probably they are singing him cause Toni Kroos will retire soon, and they might find him as a suitable replacement for Kroos. but you know, there are a lot of better players in the Real Madrid squad. So Khephren Thuram will literally have to pray that a teammate of him gets injured or something so that he can play😅. Otherwise, it is going to be very tough for him to actually be able to get a chance to play in the Los Blancos squad.
So from that point of view, it is going to be better for Khephren Thuram to go to another club, he will get a good amount of playtime. Juventus does seem to be a good destination. But the thing is if he is able to show good performance if he does go to Los Blancos, maybe Ancelotti will consider him at least as a bench player until the Euros end and Kroos hangs up his boots. I think the biggest thing is to perform well, no matter where you are. That is going to give you the biggest chance to play wherever you want.