@syofiaa
A few things to remember.
It's a marriage to protect her, so whether he's the ml is still somewhat up in the air, he even told her that if she falls in love with someone he'll be fine with it no questions asked, he's marrying her to protect her, not because he's in some form of emotional relationship with her.
Now this doesn't discount that he could be the ml, but so far we haven't seen anything concrete to suggest that, and even if he is, it doesn't mean they won't fall for each other until much later.