Max had always had a place for Kate, but it was never one of a sibling. She had been treated horribly when she was growing up as a second class member of the family by his mother. He had lost a lot, if not all respect for the woman because of that. When Kate took a stand, he was right there to back her up this time. He also realized that she had grown up when he was not looking in her direction and she was beautiful. He knew he was playing with fire, but he really wanted to get burned this time.