How was Richard III related to King Edward IV?

Richard III was the younger brother of King Edward IV. Both were sons of Richard, 3rd duke of York, and his wife, Cecily Neville.1

As the younger brother, Richard III served as a loyal supporter during much of Edward IV's reign. Following Edward IV's death in 1483, Richard III eventually usurped the throne from his nephew, Edward V—who was Edward IV's eldest son—by claiming that Edward IV's marriage was invalid and his children were illegitimate.123