The Wars of the Roses

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York: "Ruling house of England (1461-1485), including Edward IV, Edward V, and Richard III. During the Wars of the Roses its symbol was a white rose."

Lancaster: "English royal house that from 1399 to 1461 produced three kings of England—Henry IV, Henry V, and Henry VI. During the Wars of the Roses its symbol was a red rose."

(From the American Heritage Dictionary)