Which character is Tommy's daughter with Lizzie Shelby?

Ruby Shelby is Tommy Shelby’s daughter with Lizzie Shelby.

Lizzie Stark, formerly a sex worker in Small Heath, eventually becomes Tommy’s secretary and then his second wife. Their daughter Ruby is born into the Shelby household and becomes one of the most emotionally important figures in Tommy’s later story.

Ruby is not to be confused with Charles Shelby, Tommy’s son with Grace, or Karl Thorne, Ada and Freddie Thorne’s son. Her illness in series 6 prompts Tommy to return to England after he has tried to distance himself from his family. Ruby’s storyline also reflects the show’s recurring mixture of family loyalty, grief and Romani spiritual beliefs.