In 1884 a possibly unrelated George Noble Plunkett was created a Papal Count by Pope Leo XIII for donating money and property to the Sisters of the Little Company of Mary, a Roman Catholic nursing order. No connection has been established to Charles Cornelius Plunket
What I have located so far:
Charles Cornelius Plunket was born about 1772 said to be of Waterford, Ireland.
On 31 Jan 1805 Charles married Harriet Villebois/Villebors/Villibers at Lymington, Hampshire. They had two children:
. Charles Francis Plunkett (1805 Malta – 1807 Malta) d.inf
. Harriet Maria Elizabeth Plunkett (1809 Malta – 1864)
Harriet Plunket nee Villebois died on 6 Oct 1821 at Rosehill House Milbrook, Southampton, Hampshire, England.
Charles Cornelius Plunket was married secondly in 1825 to Mary Josephine Green at Southampton, Hampshire, England. They had three children:
. Charles Thomas Cornelius Plunket (1826-1902) m. Mary Clara Mullaly (1823-1910) daughter of Thomas Mullaly (1791-1843 and Jane Hudson (1793-1858)
. James Francis Truman Plunket (1831-1917) m. Catherine Marie Prestage (1835-1917)
. Mary Jane Plunkett (1834-1916) m. Michael J Keogh (1827-1874) son of Ignatius Keogh (1772-1851) and Frances Arabella French (1790-1862)
Charles and James are styled as "Count" in their obituaries/BDM notices.
Charles Cornelius Plunket died 19 Apr 1838 aged 66 at Southampton, Hampshire, England.