Does Sherlock Have a Sister?

Eurus Holmes is the younger sister of Mycroft and Sherlock Holmes who was completely unknown to Sherlock until her reveal in "The Lying Detective".

Is Sherlock's sister eurus or Enola?

In Netflix's adaptation of Enola Holmes, Enola is Sherlock's younger sister. Sherlock (Henry Cavill), Mycroft (Sam Claflin) and Enola (Millie Bobby Brown) are the children of Eudoria Holmes (Helena Bonham Carter), although due to the large age gap between Enola and her brothers, the 16-year-old barely knows them.

Does the real Sherlock have a sister?

Enola Holmes is actually Sherlock Holmes's sister.

Her brothers, Sherlock and Mycroft, are also in the movie—obvs—although Mycroft existed in the Sherlock canon going all the way back to the original Sir Arthur Conan Doyle stories.