Catherine (Kitty) Britton was believed to be the daughter of an Anglican clergyman who was the military chaplain for the garrison at Fermanagh in the North of Ireland. She renounced the church at the beginning of the 19th century which her forefathers had followed for over 200 years, and returned to the church of her earlier ancestors, to the Holy Catholic faith and married an outstanding young catholic captain Stephen Cassidy.  This suggests she may have married some time around 1800. We know she had at least one brother Thomas, living at Mullaghdun Townland in abt 1828 with his son.
Three of her sons Thomas, Phillip and Edward were transported to Australia in 1830.
The death certificates of two of her sons, Thomas and Phillip, indicate their mothers name unknown BRITTON/BRITTEN so it is not confirmed her name is actually Catherine. Other variations of her name are Kitty and Katy.
The James CASSIDY who emigrated to the US and married Margaret McELROY is also a son of Catherine and Stephen. This has now been confirmed through DNA testing. Her name is recorded in the US family bible as Kitty.
It is also possible that she was dead by the time of sons' transportation. There are no references to her in newspaper accounts or the serialised story in the newspaper. This could account for why her name was not known by the informants of Thomas and Phillips death.
The surname of Britton was first found in Devonshire, where they were seated from the 11th century. Britton is originally believed to be a French name. Often from County Tipperary, County Kildare and County Meath.
The name was only linked with the Parish of Boho Co. Fermanagh in the early 1800s. The Britton's were prominent members of the Church of Ireland (non Catholic) and were recorded as Sidemen in the Boho church back in the 1700's. 
DNA matches have confirmed the ancestry back to this shared ancestor of Catherine BRITTON due to an X chromosome triangulated group, from the descent lines of two of her sons Thomas and James. You can read more about my DNA research of Catherine on my blog, please click here.
Whilst relationships have been confirmed back to this ancestral couple of Stephen CASSIDY and Catherine BRITTON as a result of multiple autosomal matches from the descent lines of three of their sons Thomas, James and Phillip, it is still unclear whether the segment matches on Chromosome 1 belong to Stephen or Catherine.
There is a Catherine CASSIDY listed as a widow in England 1861 census at St Oswalds Chester. She is aged 80, this would make her b1781, living with an Ann (born Longford Ireland) and Michael McEvoy (born Kilkenny Ireland) stated relationship mother in law. (Son James is believed to be married to Margaret McELROY). Could this be her?
If you know the answer to either of these questions please contact Veronica Williams.
↑ Fr Peter Charles Klein SYD, Life of Father Philip Cassidy, PP Archdeacon, Benedictine Monks, Arcadia, NSW, Fr Peter Charles Klein SYD.
↑Gedmatch X match one to one comparison confirmation of relationships between T766864, T410351 and A969300; resulting in Triangulated segment = 14 cM, Chromosome 23, 99.7-115.4, 30 Dec 2016.
Australia Death Index, 1787-1985 (Online publication - Provo, UT, USA: Ancestry.com Operations, Inc., 2010.Original data - Compiled from publicly available sources.Original data: Compiled from publicly available sources.), Ancestry.com, http://www.Ancestry.com, Database online.
The Church of Jesus Christ of Latter-day Saints, Ancestral File (R) (Copyright (c) 1987, June 1998, data as of 5 January 1998), Family History Library, 35 N West Temple Street Salt Lake City, Utah 84150 USA. Ancestral File Number: C85S-HB
Thank you to Veronica Williams for creating WikiTree profile Britton-641 through the import of CASSIDY and SWEENEY 4_2013-08-13_2013-08-16.ged on Aug 16, 2013. Click to the Changes page for the details of edits by Veronica and others.
It may be possible to confirm family relationships with Catherine by comparing test results with other carriers of her mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Catherine: