In Oct 1870 Arthur George Onslow 3rd Earl Onslow 1777-1870 (age 92) died. His great nephew [her father] William Onslow 4th Earl Onslow 1853-1911 (age 17) succeeded 4th Earl Onslow, 4th Viscount Cranley, 7th Baron Onslow, 8th Baronet Onslow of West Clandon in Surrey, 9th Baronet Foote of London. [her mother] Florence Coulston Gardner Countess Onslow 1853-1934 (age 17) by marriage Countess Onslow.
In 1875 [her father] William Onslow 4th Earl Onslow 1853-1911 (age 21) and [her mother] Florence Coulston Gardner Countess Onslow 1853-1934 (age 21) were married.
On 22 Jul 1881 Gwendolen Florence Mary Onslow Countess Iveagh was born to William Onslow 4th Earl Onslow 1853-1911 (age 28) and Florence Coulston Gardner Countess Onslow 1853-1934 (age 28).
In Jul 1903 [her future brother-in-law] Arthur Ernest Guinness (age 26) and Marie Clothilde Russell were married at St George's Church, Hanover Square. He the son of Edward Guiness 1st Earl Iveagh 1847-1927 (age 55) and Adelaide "Dodo" Guinness Countess Iveagh 1844-1916 (age 59). She a great x 5 granddaughter of King Charles II of England Scotland and Ireland.
Before 15 Oct 1906 Rupert Edward Cecil Lee Guinness 2nd Earl Iveagh 1874-1967 (age 32) and Gwendolen Florence Mary Onslow Countess Iveagh (age 25) were married. She by marriage Countess Iveagh. She the daughter of William Onslow 4th Earl Onslow 1853-1911 (age 53) and Florence Coulston Gardner Countess Onslow 1853-1934 (age 53). He the son of Edward Guiness 1st Earl Iveagh 1847-1927 (age 58) and Adelaide "Dodo" Guinness Countess Iveagh 1844-1916 (age 62).
On 23 Oct 1911 [her father] William Onslow 4th Earl Onslow 1853-1911 (age 58) died at Hendon Barnet. His son [her brother] Richard William Alan Onslow 5th Earl Onslow 1876-1945 (age 35) succeeded 5th Earl Onslow, 5th Viscount Cranley, 8th Baron Onslow, 9th Baronet Onslow of West Clandon in Surrey, 10th Baronet Foote of London. Violet Marcia Bampfylde Countess Onslow 1884-1954 (age 26) by marriage Countess Onslow.
On 08 May 1912 [her son] Arthur Guinness was born to [her husband] Rupert Edward Cecil Lee Guinness 2nd Earl Iveagh 1874-1967 (age 38) and Gwendolen Florence Mary Onslow Countess Iveagh (age 30).
On 07 Oct 1927 [her father-in-law] Edward Guiness 1st Earl Iveagh 1847-1927 (age 79) died. On 07 Oct 1927 His son [her husband] Rupert Edward Cecil Lee Guinness 2nd Earl Iveagh 1874-1967 (age 53) succeeded 2nd Earl Iveagh.
On 03 Aug 1934 [her mother] Florence Coulston Gardner Countess Onslow 1853-1934 (age 81) died.
On 08 Feb 1945 [her son] Arthur Guinness (age 32) died.
On 22 Mar 1949 [her brother-in-law] Arthur Ernest Guinness (age 72) died.
On 16 Feb 1966 Gwendolen Florence Mary Onslow Countess Iveagh (age 84) died.
On 14 Sep 1967 [her former husband] Rupert Edward Cecil Lee Guinness 2nd Earl Iveagh 1874-1967 (age 93) died. His grandson Benjamin Guinness 3rd Earl of Iveagh 1937-1992 (age 30) succeeded 3rd Earl Iveagh.
Paternal Family Tree: Onslow
Kings Wessex: Great x 25 Grand Daughter of King Edmund "Ironside" I of England
Kings Gwynedd: Great x 22 Grand Daughter of Owain "Great" King Gwynedd 1100-1170
Kings Seisyllwg: Great x 27 Grand Daughter of Hywel "Dda aka Good" King Seisyllwg King Deheubarth
Kings Powys: Great x 23 Grand Daughter of Maredudd ap Bleddyn King Powys 1047-1132
Kings England: Great x 16 Grand Daughter of King Edward III of England
Kings Scotland: Great x 20 Grand Daughter of William "Lion" I King Scotland
Kings Franks: Great x 21 Grand Daughter of Louis VII King Franks
Kings France: Great x 18 Grand Daughter of Philip "The Fair" IV King France
Great x 4 Grandfather: Arthur Onslow 14 x Great Grand Son of King Henry III of England
Great x 3 Grandfather: George Onslow 1st Earl Onslow 1731-1814 15 x Great Grand Son of King Henry III of England
Great x 2 Grandfather: Thomas Onslow 2nd Earl Onslow 1754-1827 12 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: John Shelley 4th Baronet 13 x Great Grand Son of King Edward III of England
Great x 3 Grandmother: Henrietta Shelley Countess Onslow 1731-1802 11 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Margaret Pelham Lady Shelley 10 x Great Grand Daughter of King Edward III of England
Great x 1 Grandfather: Thomas Cranley Onslow 13 x Great Grand Son of King Edward III of England
GrandFather: George Augustus Cranley Onslow 14 x Great Grand Son of King Edward III of England
Great x 1 Grandmother: Susannah Elizabeth Hillier
Father: William Onslow 4th Earl Onslow 1853-1911 15 x Great Grand Son of King Edward III of England
GrandMother: Mary Harriet Anne Loftus 
Gwendolen Florence Mary Onslow Countess Iveagh 1881-1966 16 x Great Grand Daughter of King Edward III of England
Great x 2 Grandfather: Alan Gardner 1st Baron Gardner
Great x 1 Grandfather: Alan Hyde Gardner 2nd Baron Gardner
GrandFather: Alan Legge Gardner 3rd Baron Gardner