ROCKPORT — The family of the surviving passenger in a December car crash that killed two teenagers has notified the town it will file a lawsuit against the town and police department. The notice claims negligence on the part of a police officer who pursued the teens, which the family says resulted in the collision. Caleb Byras, 17, of Litchfield, and Kara Brewer, 16, of Rockland, were killed when the Subaru station wagon Byras was driving went off the road and struck a tree on Wotton’s Mill Road in Union about 11:45 p.m.