In 1650 Thomas Fitzwilliam 1st Viscount Fitzwilliam (age 69) died. His son Oliver Fitzwilliam 1st Earl Tyrconnel (age 40) succeeded 2nd Viscount Fitzwilliam of Mount Merrion House in Dublin. Eleanore Holles Countess Tyrconnel by marriage Viscountess Fitzwilliam of Mount Merrion House in Dublin.

On 11 Apr 1667 Oliver Fitzwilliam 1st Earl Tyrconnel (age 57) died without issue at Merrion Castle, Mount Merrion, Dublin. Earl Tyrconnel extinct. His brother William Fitzwilliam 3rd Viscount Fitzwilliam (age 57) succeeded 3rd Viscount Fitzwilliam of Mount Merrion House in Dublin.

In 1670 William Fitzwilliam 3rd Viscount Fitzwilliam (age 60) died. His son Thomas Fitzwilliam 4th Viscount Fitzwilliam (age 30) succeeded 4th Viscount Fitzwilliam of Mount Merrion House in Dublin.

In 1704 Thomas Fitzwilliam 4th Viscount Fitzwilliam (age 64) died. His son Richard Fitzwilliam 5th Viscount Fitzwilliam (age 27) succeeded 5th Viscount Fitzwilliam of Mount Merrion House in Dublin. Frances Shelley Viscountess Fitzwilliam (age 18) by marriage Viscountess Fitzwilliam of Mount Merrion House in Dublin.

On 06 Jun 1743 Richard Fitzwilliam 5th Viscount Fitzwilliam (age 66) died. His son Richard Fitzwilliam 6th Viscount Fitzwilliam (age 31) succeeded 6th Viscount Fitzwilliam of Mount Merrion House in Dublin.

On 25 May 1776 Richard Fitzwilliam 6th Viscount Fitzwilliam (age 64) died. His son Richard Fitzwilliam 7th Viscount Fitzwilliam (age 30) succeeded 7th Viscount Fitzwilliam of Mount Merrion House in Dublin.

On 04 Feb 1816 Richard Fitzwilliam 7th Viscount Fitzwilliam (age 70) died unmarried. He was buried at St Mary Magdalene Church, Richmond [Map]. His brother John Fitzwilliam 8th Viscount Fitzwilliam (age 63) succeeded 8th Viscount Fitzwilliam of Mount Merrion House in Dublin.

In 1830 John Fitzwilliam 8th Viscount Fitzwilliam (age 77) died. His brother Thomas Fitzwilliam 9th Viscount Fitzwilliam (age 74) succeeded 8th Viscount Fitzwilliam of Mount Merrion House in Dublin.

In Jan 1833 Thomas Fitzwilliam 9th Viscount Fitzwilliam (age 77) died. Viscount Fitzwilliam of Mount Merrion House in Dublin extinct.