She probably spent her childhood at Fotheringhay Castle, though she is named as being at Fastolf's house in Southwark with her mother and two younger brothers, George and Richard in September 1460 when her father returned from Ireland.. After her father's death and the her brother Edward IV was proclaimed King in March 1461 she lived at Baynard's Castle and Greenwich, and later after his marriage to Elizabeth Woodville she was frequently at court
As an unmarried sister of the new King her marriage was a matter of diplomacy, and a number of proposals were made with various European princes including with don Pedro of Portugal, a claimant to the throne of Aragon, but he died on 29 June 1466.
Negotiations had also been ongoing for Margaret to marry Charles 'the Bold', then Count of Charolais, but later Duke of Burgundy, after the death of his second wife in September 1465, but Louis XI of France, not wanting to see England and Burgundy united, proposed other matches. Richard Neville, 'the Kingmaker', Earl of Warwick, Margaret and Edward's cousin, also favoured a French marriage and Burgundy at that time had an alliance with the Lancastrians.
After Charles succeeded as Duke of Burgundy, negotiations were renewed and on 1 October 1467 Margaret officially declared her willingness to marry him at a council at Kingston-upon-Thames. Her dowry was fixed at 200,000 écus (gold crowns), about £41,000, of which 50,000 were to be paid and the rest in three yearly installments. A treaty was signed at Bruxelles 16 February 1468, and papal dispensation issued in May.
Margaret left London on 18 June,
The marriage had no issue. There was however some speculation that she may have had an illegitimate son before marriage. Coat-12 21:59, 22 November 2013 (EST)
It may be possible to confirm family relationships with Margaret by comparing test results with other carriers of her ancestors' mitochondrial DNA.
Mitochondrial DNA test-takers in the direct maternal line: