13 Aug is in August.
On 13 Aug 1311 Alfonso "Avenger" XI King Castile was born to Ferdinand IV King Castile IV King Leon (age 25) and Constance Burgundy Queen Consort Castile Queen Consort Leon (age 21). Coefficient of inbreeding 3.60%. 
After 13 Aug 1328 William Clinton 1st Earl Huntingdon (age 24) and Juliana Leybourne Countess Huntingdon (age 25) were married. He a great x 3 grandson of King Henry "Curtmantle" II of England. 
On 13 Aug 1415 King Henry V of England (age 29) landed at Normandy [Map] at the commencement of his Agincourt Campaign.
On 13 Aug 1514 Louis XII King France (age 52) and Mary Tudor Queen Consort France (age 18) were married by proxy at the Palace of Placentia, Greenwich [Map]. Louis I d'Orléans Duc de Longueville 1480-1516, a hostage in England at the time, stood in for Louis XII King France (age 52).
On 13 Aug 1568 Bishop William Barlow (age 70) died.
On 13 Aug 1582 Theophilus Howard 2nd Earl Suffolk was born to Thomas Howard 1st Earl Suffolk (age 20) and Catherine Knyvet Countess Suffolk (age 18) at Saffron Walden [Map].NOTEXT
On 13 Aug 1651 Arthur Chichester 1st Earl Donegal (age 45) and Letitia Hicks Countess Donegal (age 25) were married. She by marriage Countess Donegal. The difference in their ages was 20 years.
On 13 Aug 1697 David Wemyss 4th Earl Wemyss (age 19) and Anne Douglas were married. She the daughter of William Douglas 1st Duke Queensberry and Isabel Douglas Countess Queensberry. He the son of James Wemyss 1st Lord Burntisland and Margaret Wemyss Countess Cromartie 3rd Countess Wemyss (age 38). They were third cousin once removed.
Before 13 Aug 1703 Wriothesley Russell 2nd Duke Bedford (age 22) and Elizabeth Howland Duchess Bedford (age 21) were married. She by marriage Duchess Bedford.
On 13 Aug 1704 John Mordaunt (age 23) fought losing his left-arm at Blenheim during the Battle of Blenheim.
Major Richard Creed was killed in action.
On 13 Aug 1705 Florence Rolle (deceased) was buried at St Peter's Church, Tawstock [Map]. Inscription: IN memory of The Lady Rolle, wife of Sr John Rolle (age 79) knight of ye Bath, ye purity of whose mind wch appeared in all ye dutys of a virtuous life, made her ye best of wives, mothers, & friends her love was like her Piety, constant & unfeigned to her last moment. she dyed Augst ye 10th 1705.
Rest pious dust thy God has hear thy prayers, Calm'd all thy sorrows & wip'd off thy tears, Thy foul doth now behold his face divine, And with ye heavenly host in confort joyn, Pitys ye senseless folly of mankind, While she enjoys an endless peace of mind.
This monument was erected by her daughtr Mrs Margaret Rolle.
Florence Rolle: On or before 27 Feb 1631 she was born to Denys Rolle (age 17) and Margaret Poulett. She was baptised at St Giles' Church, St Giles in the Wood on 27 Feb 1631. In 1648 John Rolle (age 22) and Florence Rolle (age 16) were married. They were second cousin twice removed. On 10 Aug 1705 Florence Rolle (age 74) died.
On 13 Aug 1709 William Clavering-Cowper 2nd Earl Cowper was born to William Cowper 1st Earl Cowper (age 44) and Mary Clavering Countess Cowper (age 24).
Minutes of the Society of Antiquaries. 13 Aug 1718. Mr Holmes Vice-President (age 56) brought to the Society two curious antique Roman vessels of fine earth.
Mr Rawlinson brought two [?] prints with descriptions being old pictures, one of the Court of Charles V, the other of Joan of Bourbon. Specimens of ancient [?] paintings in one large sheet of paper. Jollain excidit [?].
On 13 Aug 1767 John Perceval 4th Earl Egmont was born to John Perceval 3rd Earl Egmont (age 29) and Isabella Powlett Countess Egmont. He a great x 3 grandson of King Charles II of England Scotland and Ireland. Coefficient of inbreeding 3.20%. 
On 13 Aug 1801 George Gordon 3rd Earl Aberdeen (age 79) died. His grandson George Hamilton-Gordon 4th Earl Aberdeen (age 17) succeeded 4th Earl Aberdeen. His will provided for his illegitimate son Alexander Gorden Cavalry (age 20).
On 13 Aug 1803 Charles Douglas 6th Marquess Queensberry (age 26) and Caroline Scott Marchioness Queensbury (age 29) were married at Richmond, Surrey [Map]. She by marriage Marchioness Queensberry. She the daughter of Henry Scott 3rd Duke Buccleuch (age 56) and Elizabeth Montagu Duchess Buccleuch (age 60). She a great x 4 granddaughter of King Charles II of England Scotland and Ireland. 
On 13 Aug 1821 Walter William Brabazon Ponsonby 7th Earl Bessborough was born to John Ponsonby 4th Earl Bessborough (age 39) and Maria Fane (age 34).
On 13 Aug 1825 Philip Sidney 1st Baron De Lisle and Dudley (age 25) and Sophia Fitzclarence Baroness De Lisle and Dudley (age 29) were married. She the daughter of King William IV of the United Kingdom (age 59) and Dorothea Bland aka "Mrs Jordan".
On 13 Aug 1829 Walter Scott 5th Duke Buccleuch 7th Duke Queensberry and Charlotte Anne Thynne Duchess Buccleuch Duchess Queensbury (age 18) were married at St George's Church, Hanover Square. She by marriage Duchess Buccleuch and Duchess Queensberry. She the daughter of Thomas Thynne 2nd Marquess of Bath (age 64) and Isabella Elizabeth Byng Marchioness Bath (age 55). He the son of Charles Scott 4th Duke Buccleuch 6th Duke Queensberry and Harriet Katherine Townshend Duchess Buccleuch Duchess Queensbury. He a great x 5 grandson of King Charles II of England Scotland and Ireland. 
Before 13 Aug 1849 Martin Archer Shee (age 79). Portrait of Edward Coplestone Bishop (age 73).
Edward Coplestone Bishop: On 02 Feb 1776 he was born. In 1826 Edward Coplestone Bishop (age 49) was appointed Dean of Chester. In 1827 Edward Coplestone Bishop (age 50) was appointed Bishop of Llandaff. On 13 Aug 1849 Edward Coplestone Bishop (age 73) died.
On 13 Aug 1849 Edward Coplestone Bishop (age 73) died.
Before 13 Aug 1850 Martin Archer Shee (age 80). Portrait of Charles Henry Cust (age 37).
Charles Henry Cust: In 1813 he was born to John Cust 1st Earl Brownlow (age 33) and Amelia Sophia Hume Countess Brownlow (age 24). In 1875 Charles Henry Cust (age 62) died.
On 13 Aug 1858 Mary Thicknesse-Touchet 22nd Baroness Audley was born to George Edward Thicknesse-Touchet 21st Baron Audley (age 41) and Emily Mitchell Baroness Audley.
On 13 Aug 1868 William Thomas Orde-Powlett 4th Baron Bolton (age 23) and Algitha Frederica Lumley Baroness Bolton (age 20) were married. She the daughter of Richard Lumley 9th Earl Scarborough (age 55) and Adeliza Drummond Countess Scarborough.
On 13 Aug 1868 Adolphus Cambridge Duke Teck was born to Francis Teck (age 30) and Princess Mary Adelaide Hanover (age 34) at Kensington Palace. He a great grandson of King George III of Great Britain and Ireland.
On 13 Aug 1878 Francis Rice Trevor 5th Baron Dynevor (age 74) died. His son Arthur Rice 6th Baron Dynevor (age 42) succeeded 6th Baron Dynevor of Dynevor in Camarthenshire.
On 13 Aug 1881 Charles George Noel 2nd Earl Gainsborough (age 62) died. His son Charles William Noel 3rd Earl Gainsborough (age 30) succeeded 3rd Earl Gainsborough 2C 1841, 5th Baron Barham.
On 13 Aug 1884 Arthur Wellesley 2nd Duke Wellington (age 77) died. His nephew Henry Wellesley 3rd Duke Wellington (age 38) succeeded 3rd Duke Wellington 1C 1814, 7th Earl Mornington 1C 1760, 7th Viscount Wellesley of Dangan Castle, 3rd Viscount Wellington of Talavera. Evelyn Katrine Gwenfra Williams Duchess Wellington (age 29) by marriage Duchess Wellington.
On 13 Aug 1885 John Duke Coleridge 1st Baron Coleridge (age 64) and Amy Augusta Jackson Lawford Baroness Coleridge were married. She by marriage Baroness Coleridge of Ottery St Mary in Devon.
On 13 Aug 1899 Henry Hotham 7th Baron Hotham was born to Henry Edward Hotham (age 44).
On 13 Aug 1900 Edward Littleton 5th Baron Hatherton was born to Edward Charles Rowley Littleton 4th Baron Hatherton (age 32).
On 13 Aug 1905 Emily Theresa Stern Baroness Sherborne (age 59) died. On 18 Jul 1919 Edward Lenox Dutton 4th Baron Sherborne (age 88) died. His brother Frederick Dutton 5th Baron Sherborne (age 65) succeeded 5th Baron Sherborne. Monument in Saint Mary Magdalene's Church, Sherborne [Map].
Emily Theresa Stern Baroness Sherborne: Edward Lenox Dutton 4th Baron Sherborne and she were married. On 21 Apr 1846 she was born to Hermann Stern. On 08 Mar 1883 James Henry Legge Dutton 3rd Baron Sherborne (age 78) died. His son Edward Lenox Dutton 4th Baron Sherborne (age 51) succeeded 4th Baron Sherborne. Emily Theresa Stern Baroness Sherborne (age 36) by marriage Baroness Sherborne.
Edward Lenox Dutton 4th Baron Sherborne: On 23 Apr 1831 he was born to James Henry Legge Dutton 3rd Baron Sherborne (age 26) and Elizabeth Howard Baroness Sherborne (age 28). Coefficient of inbreeding 6.25%.
Frederick Dutton 5th Baron Sherborne: On 28 May 1840 he was born to James Henry Legge Dutton 3rd Baron Sherborne (age 35) and Elizabeth Howard Baroness Sherborne (age 37) at Bibury, Gloucestershire. Coefficient of inbreeding 6.25%. NOTEXT On 02 Jan 1920 Frederick Dutton 5th Baron Sherborne (age 79) died. His nephew James Dutton 6th Baron Sherborne (age 46) succeeded 6th Baron Sherborne.
On 13 Aug 1907 William Waldorf Astor 3rd Viscount Astor was born to Waldorf Astor 2nd Viscount Astor (age 28) and Nancy Witcher Langhorne Viscountess Astor (age 28).
On 13 Aug 1930 David George Pratt 6th Marquess Camden was born to John Pratt 5th Marquess Camden (age 31).
On 13 Aug 1993 George Herbert 7th Earl of Powis (age 68) died. John Herbert 8th Earl of Powis (age 41) succeeded 8th Earl Powis 3C 1804. Katharine Odeyne de Grey Countess Powis by marriage Countess Powis.