You don't think that in Ireland there wasn't the use of family names through generations, sometimes 4 or 5 generations of the same names, it is one pointer to a related family. You are
lucky to have the unusual name of Simon, it was quite an unusual name when everyone was called John, James, Patrick, Thomas.
I have the Latter Day Saints CDs (no longer available)
with births of Rock/Rocks in Armagh from 1866-1874
Mary Anne Rocks born 17 Feb 1872 #60 Keady Civil Reg. Distr.
Fa: Patrick Rocks Mo: Alice Montgomery LDS microfilm#255839
Let me know if any of your Rocks fit in those years, the parents would of been born in the 1840-50's. There are 60 of them.
James Rock 21 married Martha Littlewood 18 May 13, 1851
Newtown Hamilton, Co. Armagh
Fa: John Rock/Fa: William Littlewood #101324
Terence Rocks 24 married Elizabeth Trotter 3 May 1852, Armagh, Co. Armagh
Fa: Terence Rocks/ Fa: John Trotter #101332
Mary Jane Rock 21 married Jacob McClure 21 3 Mar 1854,
Seagoe, Co. Armagh
Fa: Denis Rock Fa: James McClure