O'Mahony Ancestors

I am doing research on my mother's family.  She was Johanna O'Mahony (b.1921) in Cork City. She was the daughter of James O'Mahony (b.1898?) & Annie Mitchell (b.1899).  James was one of the 8 children of Patrick O'Mahony (b. 1860 or1849?, died 1849?) and Ellen Walsh (b.1864); MaryEllen, Jane, Jerimaih, Julia, Theresa, John, James and Joseph.

For the following I am not at all sure I have the correct names, dates or locations - Patrick ( born in Carrignavar?) was one of the 5 children of Thomas O'Mahony (b.1805 or1810, died 1892?) and Norah Cotter? (no dates); Michael, Patrick, Julia, John & Ellen.  Thomas, Norah and all the children, except Patrick were supposed to have emigrated to the US. eventually living in Pennsylvania. USA.

Thomas was one of the 4 children of John O'Mahony (b.1789? in Inniscarra or Inishcarra, died 1868?) and Anne Ivers (no dates); Michael, Thomas, Ellen & John.  He was supposed to have had his lands taken from him for some reason, left the country and when he/they returned they went to Carrignavar,

John was supposed to be one of 5 children of Andrew Mahony (b.1740?) and Catherine Mc Carthy(no dates); Paul, John, Elizabeth, Delia, & Martin in Gougane Barra. The old info I was given said he died in the Seige of Limerick, but the dates don't match up.

If anyone has any info that would be very much appreciated.  I will be in Cork mid June 2014, if anyine has info I can meet you at the University College Cork-UCC.

Thanks