Louise marries Joseph Wojtkiewicz, who works at a college, and has a reputation for being a ladies' man.
She met him when he came asking for help so she could treat his 6 year old son who had a fever of 105. He had a set of twin girls, as well, and he was a widower.
The one thing that may have attracted Louise to him was his paternal tendencies. He was very loving to his children equally. This might have rubbed on her, since she was also one of a set of twins, but her parents had devoted all their attention to her sister. She might have also been attracted by the attention he emphatically placed on his children, as she loved her father very much, and missed him immensely.
Thus, the paternal quality of Joseph was her most preferred feature. Remember, this is not a love story, but a story of finding your true place within. Joseph was one of those characters who helped her mold her persona.