Shelly Wu, six, and Lily, seven, were hit near the Grove Lane and Antrobus Road junction, Handsworth, last June.
Michael Junior, 35, from Handsworth, admitted two charges of causing death by dangerous driving and three charges of causing serious injury by dangerous driving, at Birmingham Crown Court.
Junior will be sentenced at the same court on Thursday.
The crash caused serious injury to Shelly and Lily's mother, Zhulan Wu, and her other two children.
More on this story and others on Birmingham and Black Country
Sgt Steve Newbury from West Midlands Police said: "This tragedy rocked the local community and devastated a family. Lily and Shelly's mum continues to recover from serious head injuries."
He added the children who survived have recovered from their injuries but continue to suffer "emotional trauma".
Judge Murray Creed imposed an interim driving ban on Junior, of Copthall Road, and granted him bail until Thursday, when he will reappear in court.
A man has pleaded guilty to causing the deaths of two sisters in a road crash in Birmingham.