SELECT
  COUNT(*) as number
FROM
  (
    SELECT
      f.id as id2
    FROM
      final_car_user f
      INNER JOIN final_car_user f1 ON f.first_name = f1.first_name
      AND f.last_name = f1.last_name
    group by
      (f.id)
    HAVING
      count(f1.id) > 1
  ) as t1