Monsell was born to William Monsell (1778–1822), of Tervoe, Clarina, County Limerick, and Olivia, daughter of Sir John Johnson-Walsh, 1st Baronet, of Ballykilcavan.
The provided text describes the parentage of Monsell. It states that he was born to William Monsell and Olivia, daughter of Sir John Johnson-Walsh, 1st Baronet, of Ballykilcavan.