Because he's an Omega, they could marry him off to someone else to make a business connection. That was the intention of his engagement to ML. But there seems to be a ground hog day kind of thing going on, too. ML remembers events from a previous run through and MC gets flashes of them in his dreams. That's why ML does things like telling him not to go to the greenhouse and just stay inside because he knew he would collapse in there. It's also why ML showed up when his brother tried to SA the MC. Because he knew it was going to happen, but from the flash MC got of it, it seems like he actually got R**ed by the MLs brother. ML knows what's going to happen, but only up to a point because he's changing things.
Wow, what a calculating bastard (づ￣ ³￣)づ thanks
Why did he took him in anyway if they won’t see him as family? Is there a reason for that in the novel?