William Salter and Agnes ONeil

My ancestors William Salter and Agnes ONeil were, according to Agnes' death certificate, married in Castlecomer approximately 1828.  There were seven children born between 1829-1845;

Thomas

John - travelled to Australia 1856/7 with wife Anastasia (nee Murphy) and his sister Margaret

Sarah - travelled to Australia 1854 and married Pierre Descrimes 1856

Margaret - travelled to Australia 1856/7 with brother John and his wife

William - possibly died in Ireland before the rest of the family left

Peter

Martin

Agnes and three of her sons, Thomas, Peter and Martin, travelled to Australia in 1858.  Unfortunately Agnes died the following year and her death certificate states that William Salter her husband is deceased.  I am not sure if William (Snr) had come out to Australia earlier or had died in Kilkenny before the rest of the family left.  His son Martin's obituary states William was with the Royal Irish Constabulary but the majority of the children's marriage certificates list him as a farmer.

Does anyone have connections to this family or know where the Williams (Snr and Jnr) were buried?