Searching for ancestors

I am searching for any further information on My great grandfather John Cavanagh who was born in 1840 in Ireland.  His father John Cavanagh died six weeks after he was born.  He left for Australia on the Golden Dream in 1863 arriving in Brisbane in May of that year.  On the passenger ship list the name was spelt Kavanagh.  He was single when he arrived and he married Mary O'Dea in Warwick Qld in 1867.  He died in 1924 at age 84 and is buried in the Warwick cemetery in Qld Australia.  On the marriage certificate the name is spelt Cavanagh.

On his marriage certificate it states that he came from Kilcommon Co Tipperary.  His parents were John Cavanagh and Margaret Conden.  In his death notice it states that he had two siblings, Thomas who it states lived in USA and a sister Ann who settled in New South Wales.

This year on the weekend 27/28 September we are having a family reunion in Allora near Warwick to celebrate his arrival in Australia 150 years ago.  Up until now we have not been able to find the place of his birth or the burial site of his parents, John and Margaret nee Conden.  I imagine that they were born in the early 1800's.  

We have not been able to trace any connections with Thomas or Ann.

With appreciation for any connections or information.  I am presently in Ireland until 5 June and just found the reaching out brochure.

Monica Cavangh.