facts. he just wants diana to be happy and the fact that he knows that she dies brutal deaths in the game just makes him protective bro is NOT trying to get with her romantically
He's still being a creep though. Even if he doesn't want to marry Diana, doesn't wanting to marry a woman who doesn't love Diana as much as he loves her and understand and accept that Diana is more important than her in their marriage is basically saying he is obsessed with her and want someone who won't get in the way. He might as well just Diana herself at this point. The parents are right (for once). I would also be concerned if my children would be acting like that and want to separate them
little spoiler
I kinda skimmed through the novel a little bit and it's really slow, there isn't much in term of romance for now. And I don't think the og FL is Cain love interest but you are right, she is nice ( and a bit silly ). She'll become one of their friends but she misanderstand and thinks Diana is the one reincarnated like her, if I remember correctly.
But yeah as far as romance go, Cain has some "moments" with Ilvareno, I guess... could just be baiting though.
Fun fact: Diana's dream about being a knight is gonna be one of Cain main objectives. Like he's gonna think about how to go about making it legal and acceptable for the public opinion and stuff ( girl knights exist but it is very rare and they are commoner not noble ).
"I hope this isn't going the sis-con route!!" It clearly isn't. The author knew that it would be a concern in this genre, so they put the whole "I want Diana to marry someone who makes her happy." scene in there. He's affectionate and easily excited, but he never treats her possessively and even scolds his father for objectifying her. The reason why people misunderstand him in the story is, that no one but him knows that Diana's life is in dangers. He even treats Al as a sad little kid, and not as a rival in love. It doesn't get clearer than "If they were to fall in love and marry, I'd have nothing against it.", he doesn't want to marry his sister, he wants his sister to not get murdered.
Anyway this is really interesting, and I think one of the better "reincarnated into a loving family" stories. The characters aren't reduced to ideal Arents who provide unconditional love and affection to their children, but they aren't cruel or abusive either. They have flaws that lots of parents have (comparing children, scolding children for something they encouraged, using children to appease superiors), but they still love them dearly. I understand why they're concerned about their relationship, because they just don't have the same info as we do. I like that Cain's idea of nobility, while good, is clearly false. His parents somewhat scorn commoners and free expression, but they're not the ones who are wrong about what nobles are like, Cain is, yet it's his ideas that make Diana a kinder lady.
In a way, it's a bit more mature look at nobility, than all those shoujo manhwas, where commoners are only there to virtue signal that the FL is a good person, while she continues to muck around with the emperor, forgetting about them as soon as they're out of frame.
I especially liked the cake eating scene. In other stories, the scene would be used to illustrate how loving the father is to his daughter, but here he's depicted as wasteful.
On a final note, if there's going to be romance, I think it'll be with the original FL, because so far she seems really nice, and I think Cain wants to talk to someone about video games lol.