Background Mayer-Rokitansky-Küster-Hauser syndrome is a rare entity with proposed genetic underpinnings. Ovarian carcinoma has well-described genetic associations and syndromes, although much of the etiology of the disease remains unknown. Cases Two sisters present in the 1970s with primary amenorrhea, 46, XX karyotypes, and absent uteri consistent with MRKH syndrome. In the 2010s, both sisters again present for care. Case 1 presents one sister with stage IIIC serous ovarian adenocarcinoma and negative BRCA panel. Case No 2 presents the other sister with stage IIIC serous ovarian adenocarcinoma and a negative panel for 32 genetic variants associated with ovarian carcinoma. Conclusion The familial association of two rare diseases and negative genetic workup could point to a new genetic understanding of reproductive structure development and ovarian carcinogenesis.