Did Medusa have any siblings

Medusa was the youngest of three sisters, called the Gorgons. Of the three, she was the only one born mortal and beautiful, even by divine standard. Her sisters were monstrous, and immortal, making them a force to be reckoned with. When Medusa was punished for allowing Poseidon to have his way with her in Athena's temple, where she was a priestess, Athena punished her by making her even more horrible than her sisters, giving her their serpentine form, but also snaked for hair, making her so horrible to behold, that any who did were immediately turned to stone.

It is a common misconception that ALL the Gorgons has this power, but only Medusa is noted as actually having done so. Stheno and Euryale personified the dangers of the sea (their father was the primordial god of the sea, Phorcys, who preceaded Okeanos and Poseidon) and while terrible to behold, did not have a petrifying gaze.