Appears they married in Dublin in 1876 source:
http://pilot.familysearch.org/recordsearch/start.html#p=homeJohn Neilan
Registration District: Dublin South
Date: 1876
Volume 7 Page 661
Eva Kelly {same registration details}
You could order marriage record from
www.groireland.ieInclude the above information and a photocopy will only cost four euro. The form is not designed to include some of the information but include it where you can.
Also found few more births source:
www.familysearch.orgAnne Neilan
10-Dec-1878 Roscommon
Daughter of John Neilan and Eva Kelly
John Neilan 30-Apr-1877 Roscommon
Son of John Neilan and Eva Kelly Kilteevan Roscommon
(another record on same website says Birth 1st May 1877 Baptised 6th May 1877)
Evalen Anna Neilan birth: 20th Feb 1880 Baptised: 27 Feb 1880 Kilteevan Roscommon
daughter of John Neilan and Eva Kelly (Evalen is another form of Valentine i think)
This appears to be Eva's death
Eva Neilan
Registration District: Dublin South
Jul-Sep 1930
Estimated Birth Year: 1857
Age 73
Volume 2 Page 199
Ger