They may have been born in Ireland but possibly they married over here, which means you can obtain their marriage certificate and that will help give you their respective father's names. On the 1911 census were they already married and living together or have you found them living as single people with their families?
Have you found them or their family living in England on the 1901 census? I would need to know their ages really to advise on what Irish records you can look at.
Most Irish census returns were destroyed in a fire in Dublin in 1922, but over the years a great deal of effort has been put into compiling alternative sources for research.
This is a good site that gives you an outline of civil sources:
http://www.groireland.ie/history.htm#THE%20BEG INNINGS%20OF%20REGISTRATION
For census substitutes of Dublin this link shows the sparsity:
http://www.irishtimes.com/ancestor/browse/coun ties/leinster/dublin1.htm
You should look at all the members of the family to see if amy of them prior to 1911 were already in England.