"Kate is also Elena's daughter," Derek added since Stiles left that part out. It probably sounded incredibly confusing to Cora and he realized that he should have explained some of this to her prior to dinner. "She's from Elena's future though."
There were a lot of werewolves around and he hoped that his sister would join the rest of the community. He was hardly a joiner, but it was nice to have that sense of belonging that had been missing from his life for so long since the fire.