The Titanic's twin sister, the Britannic, was bigger and better built, but she sank to the bottom three times faster. Why she sunk has remained a mystery until now.The Titanic's twin sister, the Britannic, was bigger and better built, but she sank to the bottom three times faster. Why she sunk has remained a mystery until now.The Titanic's twin sister, the Britannic, was bigger and better built, but she sank to the bottom three times faster. Why she sunk has remained a mystery until now.