Isabella Swan may have seemed to be an only child but she was not. When Charlie and Renee tried to save their failed marriage but instead of having another kid, they adopted two.
Pablo and Selena are twins from an orphanage in Mexico, when they were adopted by the Swans Bella was three months old and they were five.
Now their both twenty three and Bella is eighteen. Their going to see their dad and sister for the first time in five years, but when they meet the Cullen's, specifically Carlisle and Esme, their lives will change forever.
Disclaimer; I do not own Twilight or any of Stephanie Meyers Characters, I only own my characters and the story line