In or before 1776 [his father] Neil Primrose 3rd Earl Rosebery (age 47) and [his mother] Mary Vincent Countess Rosebery (age 23) were married. She by marriage Countess Rosebery. The difference in their ages was 23 years. He the son of James Primrose 2nd Earl Rosebery and Mary Campbell Countess Rosebery.

In 1808 Archibald Primrose 4th Earl Rosebery (age 24) and Harriett Bouverie Countess Camden (age 17) were married. He the son of Neil Primrose 3rd Earl Rosebery (age 79) and Mary Vincent Countess Rosebery (age 55).

On 07 Aug 1809 Henry St John-Mildmay 4th Baronet (age 22) and [his sister-in-law] Charlotte Bouverie were married. He would later marry her sister [his wife] Harriett Bouverie Countess Camden (age 18); an example of Married to Two Siblings.

In 1815 Henry St John-Mildmay 4th Baronet (age 27) and [his wife] Harriett Bouverie Countess Camden (age 24) were married. She the sister of his first wife [his sister-in-law] Charlotte Bouverie; an example of Married to Two Siblings.

In 1819 Archibald Primrose 4th Earl Rosebery (age 35) and Anna Margaret Anson Countess Camden (age 22) were married. She by marriage Countess Camden. He the son of Neil Primrose 3rd Earl Rosebery and Mary Vincent Countess Rosebery (age 66).

In 1830 [his brother-in-law] General George Anson (age 33) and Isabella Elizabeth Annabella Weld-Forester were married.

In 1835 Charles John Murray (age 24) and [his sister-in-law] Frederica Sophia Anson (age 20) were married. He the son of David William Murray 3rd Earl of Mansfield (age 57) and Frederica Markham Countess Mansfield (age 61).

In 1837 Henry Cavendish 3rd Baron Waterpark (age 43) and [his sister-in-law] Elizabeth Jane Anson Baroness Waterpark (age 20) were married. She by marriage Baroness Waterpark. The difference in their ages was 22 years.

On 20 Sep 1843 [his son] Archibald John Primrose (age 33) and [his daughter-in-law] Catherine Lucy Wilhelmina Stanhope Duchess of Cleveland (age 24) were married. She the daughter of Philip Henry Stanhope 4th Earl Stanhope (age 61) and Catherine Lucy Smith Countess Stanhope. He the son of Archibald Primrose 4th Earl Rosebery (age 59) and Harriett Bouverie Countess Camden.

[his son] Bouverie Francis Primrose and Frederica Sophia Anson were married. He the son of Archibald Primrose 4th Earl Rosebery and Harriett Bouverie Countess Camden.