I'm a bit confused by your post ie I'm not sure which families or generations you are referring to. So starting with your statement
I am stuck on finding Phillips father Thomas Gaghen wilfe Margaret o'Tool arrived in Adelaide 1855.
I THINK THOMAS WAS BORN ABOUT 1825..?
From the
Biographical Index of South Australians 1836-1885 Not always entirely accurate but a good place to start your South Australian research if your ancestors arrived in those years. As this resource was compiled in 1986 and there are now more records available, it is a good idea to check the information.
GAGHAN Thomas born 1834 Galway Ireland
Died 30 Aug 1890 Buried West Terrace Cemetery
Arrived 1855 GRAND TRIANON Lived Adelaide, Mitcham Religion Roman Catholic
Married Margaret nee O'TOOLE Born 1834 Galway Ireland Died 18 Aug 1921
Children Annie 1855-, Philip, Julia MONAGHAN 1860-, John, Caroline, Mary, James Margaret, Emma, Edward Thomas c1877-1891
This newspaper report has the list of immigrants -
http://nla.gov.au/nla.news-article49302787However this list as mistranscribed their surname as
GALAGAN - they are both aged 21 years in 1855.
http://www.theshipslist.com/ships/australia/grandtrianon1855.shtmlIt would appear that Thomas and Margaret did not register all their children's births. It may be worth contacting the Catholic Archives in Adelaide. It seems they didn't register any of their children's birth until they lived in Mitcham.
I have transcribed the entries exactly as they appear in the birth indexes.
GHGAN John
21 Nov 1861
Father Thomas GHGAN Mother Margaret TOOLE
At Mitcham Ade 20/224
GEOGAN Catherine
1 Dec 1863
Father Thomas GEOGAN Mother Margaret TOOLE
At Mitcham Ade 31/57
GEHGAN Mary
16 Feb 1866
Father Thomas GEHGAN Mother Margaret TOOLE
At Mitcham Ade/33/504
GAGHEN Margaret
9 Sep 1870
Father Thomas GAGHEN Mother Margaret TOOLE
At West Mitcham Ade 87/344
GAGHEN Emma
12 Jan 1874
Father Thomas GAGHEN Mother Margaret TOOLE
At West Mitcham Ade 130/345
GAGHEN Edward Thomas
10 Aug 1877
Father Thomas GAGHEN Mother Margaret TOOLE
At West Mitcham Ade 187/29
The interesting thing is Eva's mum 's name was Quallman but on her marriage ceft.has put Colman her husband
Only the bride and groom's father's are noted on South Australian marriage certificates. According to the indexes Eva's mother was Clara Emma
COLMAN/COLEMAN.
GAGHEN Philip Laurance 32 years Status Widower Father Thoms GAGHEN
COLMAN Emma Clara 22 years Status Single Father Henry John COLMAN
11 May 1892
At the Registry Office, Adelaide Ade 171/649
Births
GAGHEN Eva Beatrice Annie
21 Jul 1892
Father Philip Lawrence GAGHEN Mother Clara COLMAN
At Goodwood Ade 505/180
GAGHEN Emma May
13 Sep 1894
Father Philip Lawrence GAGHEN Mother Clara Emma COLMAN
At Hyde Park Ade 549/374
GAGHEN Philip James
21 Nov 1896
Father Philip Lawrence GAGHEN Mother Clara Emily COLEMAN
At Portland Ward PtA 594/310
GAGHEN Myrtle Irene
3 Jul 1899
Father Phillip Lawrence GAGHEN Mother Clara Emma CULMAN
At Exeter PtA643/237
GAGHEN Ella Kathleen Ethel
8 Feb 1902
Father Phillip Lawrence GAGHEN Mother Clara Emma COLEMAN
At Exeter PtA 690/199
GAGHEN Florence Mira
21 Oct 1906
Father Phillip Lawrence GAGHEN Mother Clara COLEMAN
At Exeter PtA 773/490
This is obviously a mistranscription of the mother's surname. Usually information was given verbally to a local registrar.
Who registered the birth ie who was the informant on the birth certificate?GAGHEN Myrtle Clara
20 Dec 1914
Father Philip Laurence GAGHEN Mother Clara Emma QUALLMANN
At Exeter PtA 951/277 Cando