Witnesses Edward Doyle and Alice Lynch.
I feel this is an important clue. You haven't mentioned this here, but on the Catholic parish record for Helena's marriage, it gives Edward's address as 153 Townsend Street, which is the same address given for Patrick, Helena and Helena's parents, John and Bridget. This is a strong indication that Edward was a sibling of Helena.
If you look at the children of John Doyle and Bridget Kavanagh, there are at least the following:
- Elizabeth Jane Doyle, baptised 1853, St Michan's, Dublin City
-
Edward Doyle, baptised 1860, Westland Row, Dublin. Address: 3 Hamilton Row.
- Louisa Jane Doyle, baptised 1865, Westland Row, Dublin. Address: 147 Townsend Street.
- Louisa Mary Doyle, baptised 1866, Westland Row, Dublin. Address: 147 Townsend Street.
- John Joseph Doyle, baptised baptised 1869, Westland Row, Dublin. Address: 161 Townsend Street.
There are also several other possible children, whose baptism records do not contain the mother's maiden name.
The fact that the family resided on Townsend Street at least until the late 1860s is also a piece of supporting evidence (granted, they did not live at 153 exactly). I also see that Patrick and Helena had a daughter called Louisa, which is not a very common Roman Catholic name.
It all looks very plausible to me. A DNA match between you and another descendant of John and Bridget would probably be required to be 100% certain. You could also do a 'deep-dive' into the lives of John and Bridget's other children to see if that throws up any leads.
Queenie