Denis Cashman was most likely born in the late 1700's. He married Johanna Herlighy before 1817. They had at least seven children together, seven of which have baptismal records in the Register of Donaghmore Parish, Cork, Ireland. Those seven children were John born 5 January 1817 (sponsors Cornelius Herlighy and Julia McCarthy), Denis born 1 March 1821 (sponsors Cornelius Hanigan and Mary Reardon), Mary born 4 April 1823 (sponsors Michael Herlighy and Julia Shea), Cornelius born 20 April 1828 (sponsors John Cashman and Johanna Kellher), Timothy Cashman born 23 November 1830 (sponsors Johanna Connor and John Connor) died 6 July 1857 in South Scituate MA, and John Cashman b. 30 August 1833 (sponsors John Cashman and Mary Cashman). A baptismal record for their son James Cashman has not been found but James's naturalization records state he was born in North Pluckanes, Donaghmore, Cork, Ireland on 2 Feb 1820 and his death record states his parents as Denis Cashman and Hannah. The Tithe Applotment Book for Donaghmore Parish in the Diocese of Cloyne, lists John and Denis Cashman renting 56.5 acres in Pluckanes townland from a Thomas G. French Esquire in 1826. It is not known when or where Johanna and Denis died.
According to a Griffith's Valuation perambulation book dated September 5, 1850, Denis Cashman held four lots in the townland of Bunkilla totalling 47 acres 2 roods and 33 perches (47.70625 acres). These lots were variably described as "kind cold rushy pasture", "kind tillage and pasture, part exposed steep and worn", "steep, uneven, poor slaty soil, exposed." Structures upon the land at the time included a house, outbuildings, an unoccupied house and a vacant house. The total value of the holding was estimated to be 26 pounds, 2 shillings and 6 pence. Some time after the townland was perambulated by the estimator, all the immediate lessors of the townland, including Denis Cashman, were evicted and turned out by the head landlord, Henry Wise Esq., who owned the entire Townland. He threw down some of the tenants houses. Some of the tenants were promised their land again. We have no way of knowing whether or not Denis was one of the lucky ones.