still searching

Hi my name is Suz, i am currently searching for my Irish Ancestors with not much luck.  So far i have found a marriage date record and the baptism dates of the children of my Ancestors:  David Crowley and Catherine Mehegan, but now i have come to a dead end.
My family tell me that we are related to other County Cork Crowley's who emigrated to Australia but i am yet to see the connection.
Could two brothers from the same family have the first name of DAVID?
I really don't know anymore.
The other Crowley's are James and Daniel who married the EGAN sisters from Victoria, Johanna and Catherine and later moved to Trundle NSW.
My great grandfather James David CROWLEY (son of David and Catherine) emigrated to Australia aboard "southern cross" to Melbourne in 1868.
In 1873 he married Catherine CAMERON (daughter of Duncan Cameron and Flora Buchanan).  They had 7 children, then James disappeared.
I finally found his death certificate which stated the following:

Died 23 February 1900 in Corowa NSW Hospital
Occupation:  Labourer
Age:  47  which is definitely a lie!!!!!
Father:  David Crowley (farmer)
Mother:  Catherine Mehegan
Place of Marriage:  unmarried  (he was divorced from Catherine)
Cause of Death:  Haemoptysis, Aneurism of Lung
Length of Illness:  Years
Buried:  New Cemetery Corowa NSW
No Minister or Religion
Undertaker:  Charles Clayton with witnesses:  James Riley and John Jas Squires
Registered:  26 February 1900

On James David CROWLEY's emigration records he says he is 26, when really he was
31.  He was born in Kilbrittain in 1837 according to the Church records.

I presume he is in an unmarked grave.  This is my second Ancestor i have found
in an unmarked grave, it saddens me very much, nobody deserves not to have
some commemoration, even if it is just a name on a cross on the grave.

After awhile you get so sick of searching and wonder whether it was really worth looking in the first place.

I only found the marriage date and baptism dates for Catherine and David Crowley and their children through an Irish Genealogist and he said there are no more records so i guess this is the end of the trail, i certainly hope not, but for now it will have to do.

My Grandpa James Duncan CROWLEY (son of James and Catherine) was brought up by his Grandparents (Duncan and Flora Buchanan CAMERON).

I don't really know where to go now with this search!!!!!!!!!!!