Hi Maryestanle
Welcome to Ireland Reaching Out, I am assuming from the fact he had a wife he was Church of Ireland or Prostestant, the Church of Ireland can be contacted here and I have always found them very helpful. https://www.ireland.anglican.org/about/rcb-library/location-contact-det…;
If that fails the local Cavan Library or Archives may assist for him anyway as his wife died in Dublin, http://www.cavanlibrary.ie/Default.aspx?StructureID_str=1 and here http://www.cavanlibrary.ie/Default.aspx?StructureID_str=33
Also there may have been an obituary in either the local or national newspapers, the Irish Times is online since 1857, there is a subscription fee but you can purchase a day or a week etc. The British Newpaper archives have the Irish papers and there is also an Irish Newspaper Archive, all require subscription.
If they were Methodist or Baptist you could write or email there HQ for Ireland, I have contacted the Methodist Museum previously and they were most helpful.
Regards
Pat