Snell

The birth for your father in 1918 shows that he was born in Kiltegan (the townland or town) to parents George William Snell and Margaret nee Furlong and registered in Baltinglass district, his father is shown as a farmer, and he registered the birth. A check for other births to this couple doesn’t show any other later likely siblings, if there were any there were probably born after 1919 (the ~100 year) cut-off for births on IrishGenealogy.

A search for John's birth proved a little more difficult but I was eventually able to locate it by browsing the registers manually - John George Eric Snell born 11 September 1917 at Ballynatullagh townland, (order is uncertain- could be John Eric George...) parents George Snell & Margaret Furlong, family residence is shown as KIltegan, and Margaret registered the birth. It turns out that he is indexed as George Snell, with mother's surname also as Snell...

A check for marriages for the parents shows that George Snell and Margaret Furlong married at the Church of Ireland at Kilcommon on the 6th July 1915,  both full age (i.e. 21 or over) George was a widower living at Kiltegan, and Margaret's residence as Rosnastraw House, Tinahely - their fathers are noted as George Snell and John Furlong, both farmers The witnesses were Frances Greoge Furlong, Florence Edith Furlong and Thomas Furlong, probably relation of Margaret.

Rosnastraw is a townland in Kilpipe civil parish, and a search of the 1901 census see a probable match for your Margaret (as Margaret Ellen)  reported age 32, living with her brother Thomas age 26 at a house in Rosnastraw. The 1901 census shows her living with both her parents John & Mary along with 4 brothers and 2 sisters, plus a brother of her father at Ballynultagh townland, which is in Mullinacuff civil parish. Based on a search for her youngest sister Florence, the surname of Margaret’s mother Mary appears to be Chawley or similar.

Following up on George jnr. shows a likely match at Carrawaystick townland in Knockrath civil parish, he is shown as a farmer’s son age 23 ,also in the household are George snr. And a ‘daughter’ Ethel age 18 - the census for shows that Ethel is daughter of head of the household George snr. George snr. Is a widower but George jnr. Is shown as single so appears that his birth marriage was after 1911 and before July 1915.

George snr. a farmer, his wife Mary along with his son George, two daughters and brother Thomas are also shown on the 1901 census at Carrawaystick townland, all Irish Church (Church of Ireland) born County Wicklow.

A search for a birth of the youngest child Ethel, George jnr's sister, finds that she was born in September 1891 at Rathdrum, and that her mother’s surname was Hill - her mother is shown as Maria Jane on the birth. The family residence seems to be Grenane townland, probably either Greenan Beg or Greenan More townlands, which are in Knockrath civil parish to the west of the town of Rathdrum.

A check for a likely marriage of Greoge snr. and Mary (Maria Jane) Hill shows that they married  on the 23rd February 1881 at the Church of Ireland parish church in Rathdrum - George snr. Is shown as a widower living at Grenane, his father Thomas Snell a farmer deceased , the bride’s residence is Garrymore her father James Hill a farmer, also deceased. The witnesses are William Hill and Fanny Ridding

Finally a search for the first marriage for George jnr. shows that he married a Lucy Eleanor Carter on the 20th December 1911 , the groom was age 23 the bride 26, Lucy died on the 16th April 1914 at Kiltegan, the informant was her husband George Snell. The couple had at least one child - Mary Jane Snell born 14th August 1913 at Kiltegan.

ps.. might be of interest - found a very promising match for the marriage of Mary Jane Snell and an Edward Tutty on the 3rd August 1940, the marriage took place at Ballinaclash Church of Ireland.