Denis Shanahan

Hi !

I am looking for confirmation about Denis Shanahan b.1848 and at the time of his marriage (1869) to Ellen Donovan he was living in Union Hall. I believe his father was Jeremiah Shanahan and not sure who his mother was. I think Jeremiah was The Godfather to O'Donovan Rossa the Fenian.  As there are many Denis Shanahans ... and Jeremiah Shanahans ... I am looking for info to confirm my connection. 
On Denis' marriage record it lists his father as Jeremiah and Jeremiah's occupation as cartman. 
I have a mugshot of  a Denis Shanahan as he was arrested for involvement in the Fenian movement. I would like know if it is the Denis Shanahan that I speak of. I also cannot find a death record for Denis.
Ellen Donovan and Denis Shanahan had 2 children: Johanna and Patrick. Patrick married Annie Keenan  and they had 6 children. Patrick and Annie both die in 1918, leaving the children orphaned. Patrick died in Greece during WWI and Annie died of Influenza the same year.

I am not sure what happened to all the children.

I have no Info on Johanna.

Thank you!