Likely children of Catherine and Patrick McDonough. LDS BIVRI CD lists Boyle Catholic parish baptisms of Brigid McDonough 1825 and Thomas 1827. LDS film 989743 for both baptisms.
Check the 1833 LDS Tithe Applotment records for Boyle Civil parish (film 256575) and Kilbryan Civil parish (film 256624). . The 1749-1901 County Roscommon List of surnames includes many more McDonough than McCarthy in Boyle Civil parish. . Try and determine names of sibling of Catherine and Patrick McDonoughs. Also names/order of birth of children Catherine and Patrick McDonough. . See www.leitrim-roscommon.com for maps of Boyle/KilbryanRC & Civil parishes. . Don't pay a cent for Irish research until you know what you are doing.