Disclaimer: I do not own 'Hawaii Five-0' or any of the characters from 'Hawaii Five-0'. If I did own them, Steve and Danny would be shacked up in Steve's beachside home with custody of Grace and knocking boots every night.
It's not that he is emotionally stunted, no matter what Danny says, he just doesn't express his emotions the same as Danny. He keeps them hidden, locked away. It's habit. One he had to work damn hard to learn after his mother died…supposedly died, faked her death. Really, there's no way right way to phrase Doris's actions then…or now. She left him, Mary and their father. All to protect them and instead she hurt them far worse than anyone else could.
Now she keeps lying to him, to Mary, to everyone and she's dragging Catherine along with her. Catherine, the woman he is, no was with…seeing, dating, having sex with, his friend. She's still a friend, but she has betrayed him and all because of Doris. Because Doris says jump and Catherine has decided to respond by jumping. Because Catherine decided that a woman that faked her own death is a better and trustworthier person than he is.
He can't, won't forgive and forget this. He hates having someone that is so willing to betray him next to him, but he also knows that sometimes the safest place for keeping a threat is right next to him. So now he has to figure out how to explain to his true 'ohana that there is another spider to watch out for in this web of lies and deceit, a spider he unknowing brought in and exposed them to. He just hopes that they forgive him; that Danny forgives him…