Background: Richard was born on 2 October 1452 at Fotheringhay Castle, the twelfth of thirteen children of Richard Plantagenet, 3rd Duke of York and Cecily Neville at the beginning of what has traditionally been labelled the "Wars of the Roses", a period of "three or four decades of political instability and periodic open civil war in the second half of the fifteenth century", between supporters of Richard's father (a potential claimant to the throne of King Henry VI from birth)--"Yorkists"--in opposition to the regime of Henry VI and his wife, Margaret of Anjou, and those loyal to the crown ("Lancastrians"). When his father and the Nevilles were forced to flee to Ludlow in 1459, Richard and his older brother, George (later Duke of Clarence), were placed in the custody of the Duchess of Buckingham, and the Archbishop of Canterbury. When his father and elder brother Edmund, Earl of Rutland, were killed at the Battle of Wakefield on 30 December 1460, Richard, who was eight years old, and George were sent by his mother, the Duchess of York, to the Low Countries. They returned to England following the defeat of the Lancastrians at the Battle of Towton and participated in the coronation of Richard's eldest brother as King Edward IV in June 1461.
Context: Apart from Shakespeare, Richard appears in many other works of literature. Two other plays of the Elizabethan era predated Shakespeare's work. The Latin-language drama Richardus Tertius (first known performance in 1580) by Thomas Legge is believed to be the first history play written in England. The anonymous play The True Tragedy of Richard III (c. 1590), performed in the same decade as Shakespeare's work, was probably an influence on Shakespeare. Neither of the two plays places any emphasis on Richard's physical appearance, though the True Tragedy briefly mentions that he is "A man ill shaped, crooked backed, lame armed" adding that he is "valiantly minded, but tyrannous in authority". Both portray him as a man motivated by personal ambition, who uses everyone around him to get his way. Ben Jonson is also known to have written a play Richard Crookback in 1602, but it was never published and nothing is known about its portrayal of the king.  Marjorie Bowen's 1929 novel Dickon set the trend for pro-Ricardian literature. Particularly influential was The Daughter of Time (1951) by Josephine Tey, in which a modern detective concludes that Richard III is innocent in the death of the Princes. Other novelists such as Valerie Anand in the novel Crown of Roses (1989) have also offered alternative versions to the theory that he murdered them. Sharon Kay Penman, in her historical novel The Sunne in Splendour, attributes the death of the Princes to the Duke of Buckingham. In the mystery novel The Murders of Richard III by Elizabeth Peters (1974) the central plot revolves around the debate as to whether Richard III was guilty of these and other crimes. A sympathetic portrayal of Richard III is given in The Founding, the first volume in The Morland Dynasty series by Cynthia Harrod-Eagles.  One film adaptation of Shakespeare's play Richard III is the 1955 version directed and produced by Laurence Olivier, who also played the lead role. Also notable are the 1995 film version starring Ian McKellen, set in a fictional 1930s fascist England, and Looking for Richard, a 1996 documentary film directed by Al Pacino, who plays the title character as well as himself. The play has been adapted for television on several occasions.
Question: Why did he murder them?. Whats the answer?