Nephrogenic diabetes insipidus is a rare genetic renal disease characterized by insensitivity of the kidney to the anti-diuretic effect of vasopressin in spite of elevated serum antidiuretic hormone (ADH). Failure of the kidney to respond to ADH results in impaired osmoregulation and water reabsorption of the kidney, therefore, nephrogenic diabetes insipidus presents with a large amount of hypotonic polyuria, polydipsia, and dehydration. We report our experience of two familial cases of nephrogenic diabetes insipidus in brothers both having c.910+1delG in intron 2 of the AVPR2 gene with the brief review of related literatures.