Reilly, Hugh (d. 1815), merchant, was probably a son of Walter Reilly, an apothecary, of Annagh, Co. Cavan. He was a linen merchant at Cavan town by 1779, after which he ‘grew steadily in wealth and influence and became one of the most extensive catholic property owners in the county’ (O'Reilly). His rise in prosperity was due in no small part to his marriage (April 1787) to a wealthy heiress, Margaret Magaghran (1768?–1803), only child of John and Elizabeth Magaghran of Corcanidos, Milltown, Co. Cavan. John Magaghran (1726?–84), a son of Edmund Magaghran (1680?–1763), a descendant of a family who had been erenachs of St Máedóc (qv), inherited from his brother Patrick (d. 1782?), who had made a fortune in Dublin and died childless. The bulk of this fortune passed to Margaret Magaghran and so in effect to Hugh Reilly on his marriage. The couple lived at Cavan town, in 1813 at Ford Lodge, from where Reilly managed his property and engaged in other businesses. In 1790 he owned and operated a brewery. In 1792 he was a delegate from Co. Cavan at the Catholic Convention in Dublin and in 1811 was a member of the Catholic Committee. He died 29 December 1815. His family's papers survive.
By his wife Margaret (d. 1803) he had two sons and four daughters. The elder son, Walter (1792?–1838?), began his career with high expectations, entering TCD (1810), practising at the bar on the North West circuit and inheriting Annagh; but he could not manage his finances and by 1818 his liabilities had reached £10,790. He transferred ownership of his property to his brother John Edward and to avoid his creditors settled in France, at Rouen, dying there in poverty. John Edward Reilly or O'Reilly (1803–48), born at Cavan, studied at TCD, qualified as a medical doctor (1827), practised in Dublin, got his and his brother's finances in order, rebuilt Annagh House and changed his name to O'Reilly. From 1824 he was involved in politics with Daniel O'Connell (qv). Five years later the bar on catholics entering parliament was removed. In 1832 he declared his intention to stand as a Repeal candidate in Co. Cavan, issued a manifesto but withdrew. His several requests for a place on the Cavan grand jury were refused. He had an interest in local history and genealogy and contributed articles to the Nation (October–November 1842) and the Anglo-Celt (February–March 1848). His marriage (25 May 1847) to Janetta Martha Chamberlaine of Chester, whose father John was a founder of the port of Birkenhead, brought a dowry of £7,360; but the following year, on 3 September 1848, Dr John Edward O'Reilly died of cholera on a visit to Chester.