Born in Dublin, George Noble Plunkett was the son of Patrick Joseph Plunkett (1817–1918), a builder, and Elizabeth Noble (Plunkett).This image below shows George with his father Patrick Plunkett in 1860 at age 8.
The family income allowed Plunkett to attend school in Nice, France, Clongowes Wood College and the University of Dublin. At Dublin he studied Renaissance and medieval art among other topics, ultimately graduating in 1884. Plunkett spent much time abroad and throughout Italy.
In the second quarter of 1884, the same year he was created a Papal Count by Pope Leo XIII for donating money and property to the Sisters of the Little Company of Mary, he was married to Josephine Cranny. (1858–1944) and they had seven children:
Geraldine Mary Germaine (my grandmother) 1891, (Gerry),
George Oliver, 1894 (from memory, maybe '93)
Josephine Mary, 1896, (Fiona)
John Patrick, 1897, (Jack).
Biographer, politician, Irish nationalist, Papal Count via Pope Leo XIII
Count George Noble Plunkett (Irish: An Cunta Pluincéad; 3 December 1851 – 12 March 1948) was a biographer, politician and Irish nationalist, and father of Joseph Plunkett, one of the leaders of the Easter Rising of 1916 who was executed in Kilmainham Gaol on May 4, 1916.
27 Jul 1904. George was mentioned as the second beneficiary in the probate of the estate of John Joseph Cranny - his wife's father. The first beneficiary was Josephine M Plunkett. (George's wife)
23 Aug 1914 George is mentioned as second beneficiary in the will of Kate Moore with John Mangan as the first beneficiary. Not sure at this time what the connections are.
1901 census lists George Noble 48 yrs born city of Dublin and Josephine M. 42 yrs born in County of Dublin, reside house 26 in Fitzwilliam St. Upper (Fitzwilliam, Dublin) which has 14 rooms.
Another page of 1901 census George Noble Plunket signs the census form A as head of family entry states he is temporarily absent from house 7 in Kilternan Domain (Glencullen, Dublin) which has 17 rooms, 8 members of family and 3 servants. 
According to the death registration George died in the first quarter of 1949 age 97. The text of the entry being:
Event Date: Jan - Mar 1949
Event Place: Dublin South, Ireland
Registration Quarter and Year: Jan - Mar 1949
Registration District: Dublin South
Birth Year (Estimated): 1852
The birth year estimated at 1852 is an acceptable value considering he was born in the last month of 1851 according to other records. The issue is the year and age of his death.
The dates in Wikipedia look as if they are taken from Archontology.org Seoirse Pluincéad = George Noble Plunkett since that seems to be the only source of dates however neither of the two citations actually relate to the dates in question. Accordingly I believe we should use the date recorded in the registration unless other sources can be validated rather than March 12, 1948.
↑ George Plunket born in 1851 son of Pat Plunkett and Elizth transcribed entry baptism St Andrew RC Dublin
↑ "Ireland Civil Registration Indexes, 1845-1958," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FY7F-G35 : accessed 24 March 2016), MARRIAGES entry for George Noble Plunkett; citing Dublin South, Apr - Jun 1884, vol. 2, p. 595, General Registry, Custom House, Dublin; FHL microfilm 101,254.
↑ "Ireland Civil Registration Indexes, 1845-1958," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FY7N-FMQ : accessed 24 March 2016), MARRIAGES entry for Josephine Mary Cranny; citing Dublin South, Apr - Jun 1884, vol. 2, p. 595, General Registry, Custom House, Dublin; FHL microfilm 101,254.
↑ are now confirmed by Honor O Brolchain in an email. Honor O Brolchain is a granddaughter of Geraldine Plunkett Dillon. Born in 1948, she performed as a musician in the Early Music groups, The Consort of St Sepulchre's, Good Company, Pandora and Dublin Viols. She has also been a teacher all her life and has had some poetry published.
↑ "Ireland Calendar of Wills and Administrations, 1858-1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K6MR-YDC : accessed 24 March 2016), George Noble Plunkett in entry for John Joseph Cranny, 27 Jul 1904; citing 00319, 005014913, Principal Probate Registry, Dublin; 100,999.
↑ "Ireland Calendar of Wills and Administrations, 1858-1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K69Q-K3F : accessed 24 March 2016), George N Count Plunkett in entry for Kate Moore, 23 Aug 1914; citing 00612, 005014918, Principal Probate Registry, Dublin; 101,004.
↑ "Ireland Civil Registration Indexes, 1845-1958," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FTP7-GY7 : accessed 24 March 2016), DEATHS entry for George N Plunkett; citing Dublin South, Jan - Mar 1949, vol. 2, p. 396, General Registry, Custom House, Dublin; FHL microfilm 101,744.