Queen Margaret – Queen to Henry VI
Edward, Prince of Wales – their son
Lord Clifford – military commander
Duke of Exeter
Duke of Somerset (a conflation of Henry Beaufort, 3rd Duke of Somerset and Edmund Beaufort, 4th Duke of Somerset, his younger brother)
Earl of Northumberland
Earl of Westmorland
Earl of Oxford
Henry, Earl of Richmond (non-speaking role)
Somerville – messenger
Richard Plantagenet, Duke of York – asserts he should be King
Edward Plantagenet, Earl of March – later King Edward IV; York's eldest son
George Plantagenet – later Duke of Clarence; York's son
Richard Plantagenet – later Duke of Gloucester; York's son
Edmund Plantagenet, Earl of Rutland – York's youngest son
Robert Aspell, Rutland's tutor
George Plantagenet, 1st Duke of Clarence, 1st Earl of Salisbury, 1st Earl of Warwick, KG, lived from 1449 to 1478, when he was convicted of treason against Edward and apprently  drowned in a vat of wine. 
 
 George Plantagenet, 1st Duke of Clarence. Image via  Wikimedia Commons. 
 
 Encyclopedia Britannica : “George Plantagenet, Duke of Clarence”. Retrieved Online.
Henry VI Part 3 Characters of the Play