Matilda and Annie were born in New South Wales. Before they emigrated, Mathews' father, William Mathews (1798–1866), was the principal co-proprietor of Lettermuck Mill, a small papermaking business near the village of Claudy in County Londonderry. The other partners were his three brothers, Robert, Hamilton and Samuel Mathews. When first established by Robert's grandfather (also named William Mathews), Lettermuck was a successful business. Changes in papermaking technology, combined with the introduction of the Paper Excise to Ireland in 1798, adversely affected profitability. Many Irish papermakers made efforts to evade the tax on paper and the Mathews family became "notorious for crimes against the Excise". They were regularly summoned before the Court of the Exchequer to answer charges of avoidance. Between 1820 and 1826 penalties of £3,300 were imposed on William Mathews, none of which he paid. Hostile relations developed between the Mathewses and the Excise officers who regularly inspected their business. In 1833 an Excise officer named James Lampen disappeared, having last been seen entering the Lettermuck premises. A witness heard the discharge of a firearm according to a newspaper report. In March 1833 Robert's father, William Mathews, his three uncles and a journeyman employed in the mill were arrested for Lampen's murder. They were incarcerated until May that year when the charges were dropped, reportedly because of the disappearance of a key witness and the failure to find a body, despite a substantial search. It was believed within and outside the Excise office that the Mathewses were guilty of murder. From the time of the brothers' release, Excise officers, protected by an armed guard, monitored the mill around the clock. Prevented from trading illegally, the business collapsed and eventually all the brothers emigrated to various destinations. In later years, bodies were exhumed from bog near the mill, thought to belong to Lampen and an itinerant worker in the paper industry. This raises the possibility that R. H. Mathews' father and uncles were involved in a double homicide. Penniless after the collapse of the business, William Mathews and his wife Jane () falsified their ages so as to qualify for assisted migration to New South Wales. In the company of R. H. Mathews' two elder siblings, they arrived in Sydney on the Westminster in early 1840. William Mathews found labouring work for the family of John Macarthur at Camden, New South Wales and shepherded at another of their properties, Richlands