On 29 Oct 1825 Richard Wellesley 1st Marquess Wellesley (age 65) and Marianne Caton Marchioness Wellesley (age 37) were married. She by marriage Marchioness Wellesley. The difference in their ages was 27 years. He the son of Garrett Wellesley 1st Earl Mornington and Anne Hill Countess Mornington (age 83).

She one of the four Caton sisters, daughters of Richard Caton (age 62), a merchant from Baltimore, the three eldest, known as the "The Three American Graces", married European husbands husbands. Only the fourth daughter Emily Caton (age 30) had children.

Marianne Caton Marchioness Wellesley (age 37) married Richard Wellesley 1st Marquess Wellesley (age 65),

Elizabeth Caton Baroness Stafford (age 35) married George William Stafford-Jerningham 8th Baron Stafford (age 54),

Louisa Catharine Caton Duchess Leeds (age 32) married firstly Felton Elwell Hervey-Bathurst 1st Baronet and secondly Francis Godolphin Osborne 7th Duke Leeds (age 27).

Emily Caton (age 30) married Consul John MacTavish (age 38).