On 08 Aug 1863 [his father] William Henry Wellesley 2nd Earl Cowley (age 28) and [his mother] Emily Gwendoline Williams Countess Cowley (age 24) were married. He the son of Henry Richard Charles Wellesley 1st Earl Cowley (age 59).

On 17 Dec 1889 Henry Arthur Mornington Wellesley 3rd Earl Cowley (age 23) and Violet Neville Countess Cowley (age 23) were married at St George's Church, Hanover Square. She the daughter of William Neville 1st Marquess Abergavenny (age 63) and Caroline Vanden Bempte Johnston Marchioness Abergavenny. He the son of William Henry Wellesley 2nd Earl Cowley (age 55) and Emily Gwendoline Williams Countess Cowley (age 50).

On 10 Jun 1895 Charles Edward Cradock-Hartopp 5th Baronet (age 37) and [his future wife] Millicent Wilson (age 22) were married. She by marriage Lady Cradock-Hartopp.

On 12 Feb 1901 [his future brother-in-law] Charles Henry Wellesley Wilson 2nd Baron Nunburnholme (age 26) and Marjorie Cecilia Wynn Carington Baroness Willoughby Parham (age 21) were married. She the daughter of Charles Robert Wynn Carington 1st Marquess of Lincolnshire (age 57) and Cecilia Margaret Harbord Marchioness (age 44).

On 23 Jun 1904 [his future brother-in-law] Guy Greville Wilson (age 27) and Isabel Innes-Kerr (age 25) were married. She the daughter of James Henry Robert Innes-Kerr 7th Duke Roxburghe and Anne Emily Spencer-Churchill Duchess Roxburghe (age 49).

On 03 Aug 1905 Eric Chaplin 2nd Viscount Chaplin (age 27) and [his future sister-in-law] Gwladys Alice Wilson Viscountess Chaplin (age 24) were married at Warter Hall aka Priory [Map].

On 14 Dec 1905 Henry Arthur Mornington Wellesley 3rd Earl Cowley (age 39) and Millicent Florence Eleanor Wilson Countess Cowley (age 33) were married at Colombo, Sri Lanka. She by marriage Countess Cowley. He the son of William Henry Wellesley 2nd Earl Cowley and Emily Gwendoline Williams Countess Cowley (age 66). They were third cousins.

On 22 May 1911 [his brother-in-law] Guy Greville Wilson (age 34) and Avery Buxton were married.

In 1913 Henry Arthur Mornington Wellesley 3rd Earl Cowley (age 46) and Millicent Florence Eleanor Wilson Countess Cowley (age 40) were divorced. She cited "his desertion and misconduct with Mrs. Geoffrey Charles Buxton". Henry Arthur Mornington Wellesley 3rd Earl Cowley (age 46) had been named as a correspondent in the divorce suite of Geoffrey Charles Buxton against his wife.

On 19 Jan 1914 Henry Arthur Mornington Wellesley 3rd Earl Cowley (age 48) and Clare Florence Mary Stapleton Countess Cowley (age 35) were married. She by marriage Countess Cowley. He the son of William Henry Wellesley 2nd Earl Cowley and Emily Gwendoline Williams Countess Cowley (age 74).

George Montacute Neville and Florence Soames were married. He the son of William Neville 1st Marquess Abergavenny and Caroline Vanden Bempte Johnston Marchioness Abergavenny.