Louisa Molesworth was born 23 October 1749 in Dublin, County Dublin, Ireland to Richard Molesworth, 3rd Viscount Molesworth (c1680-1758) and Mary Jenney Ussher (1728-1763) and died 1 September 1824 of unspecified causes. She married William Brabazon Ponsonby, 1st Baron Ponsonby (1744-1806) 26 December 1769 . She married William Fitzwilliam, 4th Earl Fitzwilliam (1748-1833) 21 July 1823 in Bishopscourt, County Kildare, Ireland.
|Offspring of William Brabazon Ponsonby, 1st Lord of Imokilly and Louisa Molesworth (1749-1824)|
|John Ponsonby, Viscount Ponsonby (c1770-1855)|
|William Ponsonby (1772-1815)|
|Richard Ponsonby (c1772-1853)|
|Frederick Ponsonby (-1849)|
|George Ponsonby (1774-1863)|
|Mary Elizabeth Ponsonby (1775-1861)||3 March 1775||26 November 1861 London, Greater London, England, United Kingdom||Charles Grey, 2nd Earl Grey (1764-1845)|