Not for the first time Jasper wondered if it would make it a difference if Rosalie wasn't part of their family. He had a connection to each member of his family in one way or another. Love with Alice, friendship with Emmett, Edward carefully monitoring his thoughts whenever they were in public, Carlisle as his role model and Esme as his surrogate mother.
But except for the shared last name and their resemblance in looks there was no tie to Rosalie. She could just as well have been a random stranger on the street and Jasper would have felt the same emotional void he always had with Rosalie now.
But still Jasper knew, if it ever came down to it, he would stand up for her and fight for her. Because no matter how alien she might be for him, she still was family.