Just to recap on the Edgars in the 1911 census, with a view to projecting possible descendents and living relatives ...
http://www.census.nationalarchives.ie/pages/1911/Antrim/Clifton/Linwood_Street/145958/... some of the news isn't so great on Robina Agnes' siblings. Her brother 'Robert C' Edgar died in 1913:
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1913/05345/4488884.pdfHer sister 'Elizabeth R' Edgar died in 1914:
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1914/05297/4472957.pdfAfter the 1911 census, Robina Agnes gained 2 more siblings when her parents William and Isabella had Thomas in 1912 (still alive in 1969, according to a minor newspaper reference) and Isabella in 1915, but Isabella also died the same year:
https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1915/05268/4461945.pdfSome time between that death in 1915 and 1918, the family moved into a house at 12 Argyle Street, with which they were to have a long association - the relevant directory entries for Argyle Street on the Lennon Wylie website show
'12. Edgar, Wm., labourer' in 1918, 1924, 1932, 1939, 1943, and 1951, while the 1960 entry is shown as
'12. Edgar, Mrs. Isabella'.
When Robina Agnes' older sister Margaret Jane got married to a George McHenry in 1923, 12 Argyle Street was her stated address, she was recorded as the 19 year old daughter of William James Edgar a labourer, 24 year old George was recorded as the son of Thomas McHenry, a cloth dyer. With the usual health warning about online family tree inaccuracy, note that a family tree on the 'ancestry.com' website suggests that this couple went on to have a number of children - George McHenry (1903-), Mary Anne McHenry (1924-1995), James McHenry (1928-1944), Robina McHenry (1930-1996, married a Robert Samuel Townsley in 1949 and had 2 daughters Marion and Margaret), Irene McHenry (1945-2005, married a James Steritt), and Billy McHenry (1946-2009).
So plenty of scope arising from Robina Agnes Edgar's sister Margaret Jane for McHenry, Townsley and Steritt cousins.
Then there is this in 1966, note the reference to 43 Ainsworth Drive:

And this in 1981 with the same address mentioned:
