Tokyo Ghoul is best known for its tragic elements in the form of the protagonist that is Kaneki Ken. As most fans know, the amount of hardships that he endures throughout his life shape the outcome of his life as a ghoul.
Though had he not been abused and abandoned, perhaps he would be less meek, and more outspoken - being a natural good-doer and supporter of his loved ones, just like Haise is.
Inherit Naivete
Early on in the story, Kaneki Ken is already shown to have a strong moral compass, like when he refuses to kill, even if it's in self defense. In addition to this, he is always the first to give the benefit of the doubt and will even make self-sacrificing decisions to ensure that the people around him are safe. A perfect example of this is his interactions with Hinami when she's brought into Anteiku with her mother to take cover for safety. Kaneki makes the decision to befriend and even teach her kanji in addition to other academics, as she is unable to attend school.
In Tokyo Ghoul:re, Haise embodies these same traits, and because of his parental figures, Akira and Arima, he has a differing outlook on life. Rather than letting himself be taken advantage of to please another person, he instead problem-solves so that way everyone leaves the situation satisfied.
When living with his team, Haise plays somewhat of a father figure to them, cooking their meals and acting as a coach. Though he is less inclined to second guess himself, he still offers what support he can to the Quinx squad, just like Arima and Akira have to him. The "family" he had is what gave him the resolve to act on his desires to support his loved ones.
The Perfect Spouse
After Kaneki regains his memories, these aspects of his personalty stay since he now knows what a supportive family looks like. The reveal that Touka is pregnant with his child, only supports that when he proudly proclaims his love for her and how happy he is. What's more, even his slight absent-minded tendencies from when he was Haise remain. These natural traits that Kaneki possess had only been brought to light when he was reborn as Haise.
During his childhood, the way he fondly remembers his mother is almost reminiscent of someone when they're grieving. His outward thoughts were being filtered through fear of rejection and contempt. His only true parental figure, his mother, as briefly as her involvement in Kaneki's life was, had raised him to believe that the best way to be a "good person" was to let others decide for him. Circumstances that happen in one's childhood can affect the way someone turns out in adulthood, and Kaneki's habit of hiding his true feelings is one them.
Pessimist vs Optimist
Because of Kaneki's and Haise's upbringings, his outlooks on life by themselves drastically oppose each other. Arguably, the biggest difference between Haise and Kaneki are their tastes in literature. Whereas Haise still enjoys reading, Kaneki's favorite author, Takatsuki Sen's novels aren't up his alley.
When asked why the former's reasoning was because of how tragic and pessimistic all her stories were. Haise simply couldn't relate to tragedy because he wasn't consistently exposed to it. Kaneki on the other hand saw himself in her works. After all, his most notable quote in the first chapter of Tokyo Ghoul is a certain indication of his tragic mindset.