The father of Sadie and Carter, Julius Kane seems to be a mild-mannered archaeologist who writes books about ancient Egypt while traveling the world for his research, kind of like Indiana Jones. But Julius is actually a magician in the House of Life.
He blends in pretty well in the mortal world, which must help whenever he has to go through airline security. Here's how Carter describes his dad: "He has dark brown skin like mine, piercing brown eyes, a bald head, and a goatee, so he looks like a buff evil scientist" (1.14). According to Carter, he's also pretty charismatic. Carter can always tell when trouble is coming, because his dad will act nervous and clutch his workbag.
What's in his workbag, you ask? Why, his magician tools, of course. These include a staff, a wand, a lump of wax, a stylus, some inks, rope, and papyrus. Oh, and Doughboy, a talking mini-servant. We never see Julius use his magician tools, but according to Carter's memories, Julius can do some pretty powerful stuff with them, such as taking out would-be attackers or rioters.
Whatever else you might think about Julius Kane, he loves his kids. When he accidentally releases Set along with the other gods, Carter realizes that "he was intentionally keeping the fiery man's back to us, hoping Sadie and I would go unnoticed" (2.83). And once we learn enough about Set to fear him, yeah, that was a pretty brave thing for Julius to do.
Julius tells Sadie during their last conversation in the land of the living: "One of my hardest jobs as a father, one of my greatest duties, was to realize that my own dreams, my own goals and wishes, are secondary to my children's" (39.77). So while some of Julius's actions may be hard to understand, he was acting with his kids in mind. He thinks a lot about how to help them survive, attain power, and change the world for the better.
Still, it's been hard for Julius to go through with the decisions he made. He tells his kids after the fact: "Helping Osiris to his throne was a first step, a thousand times more important than anything I could've done in the world above—except being your father. And I am still your father" (41.69). It's not like he wanted to sacrifice his life and spend the rest of his time in the Land of the Dead, but he did. Even though it hurt to be away from his family.