Thank you very much Sinann. I have had a quick look at the Irish Genealogy site, very informative indeed. I'll have a good look when time permits.
On Esther, I have found a record in the Ireland Census 1901 for a Hester Bennett, aged 86 (born abt 1815), mother, widow, at House 10, Kilgarriffe, Clonakilty, Cork. Her age fits and so does the widow part. She is recorded living with Thomas aged 48, (born abt 1853), farmer and his wife Mary aged 32 (born abt 1869) with children Robert 10, Hester Anne 8, Eliza 6 and Annie 4.
Esther is recorded as Hester on Samuel's & John's Queensland Death Certificates, so I'm not overly concerned with that difference, although not sure at this stage if Hester is my Esther and if Thomas is a sibling of Samuel and John. However, there are key names, Robert, Hester, Thomas and Mary that feature in Samuel's children in Australia. Now that Church of Ireland is most likely their religion (had thought it was Catholic), hopefully that will make searching easier.
For the 1911 Census, very similar results for Thomas and Mary, no Hester now but with new child Mary aged 9, at House 12 Kilgarriff, Cork.
I'll see what information Irish Genealogy can provide.
For information prior to civil records, like birth/baptisim records for Samuel, John, Thomas, Robert & Esther, is that local parish records? And would that be (most likely) Kilgarriff Parish COI records? How do I do that?
Many thanks for any/all assistance.
Steve