He was succeeded, unopposed, in the seat by the Radical William Sharman Crawford.
[1] He inherited the castle on the death of his elder brother Matthew in 1841.
He had married in 1820 his cousin Margaret, the daughter of Dowell O'Reilly of Tullymore and had a son and heir Myles O'Reilly, who fought on the continent for the Pope and was later also an MP, and an unmarried daughter Margaret.
[2] His grandson was also named William Joseph O'Reilly (born 1864) who in turn inherited the Knock Abbey Castle estate from Myles.
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