Donovan-Kennedy Roadblock

Hi, I have been researching my family for over 20 years and have one main road block to break through. My father Finbarr Kennedy was born in Cork City in 1924 to Brian Kennedy and Mary Cox. The Cox family were all from Ballinacurra & Midleton and I have them traced to late 1700's. The Kennedy family I have traced back to early 1800's and would like to go further, many of the Kennedy's were Master Bakers and covered five generations. My grandafther Brian Kennedy was one of 12 born to James Kennedy & Mary Anne Donovan.  Mary Anne Donovan's parents were Michael and Mary Donovan unfortunately I don't have a maiden name which has caused so much trouble, I have both their death records in 1890 & 1894 which dosen't give any more clues and without that maiden name I can't confirm a marriage and also without the maiden name I cannot confirm a baptism for Mary Anne.  When my grandfather Brian's brother Jeremiah Kennedy died in 1945 a obituary published in the Cork Examiner gave some tantilising hints but I have been able to progress them further especially with regards to Donovan's, the obituary in the Cork Examiner on the 21st March 1945 said:
LATE MR. JEREMIAH KENNEDY, CORK.
The death took place with tragic unexpectedness of Mr. Jeremiah Kennedy 85 Horgan's Buildings, Cork. Deceased belonged to one of the best known and oldest families In Cork, and in addition to being a direct collateral descendant of the '98 Patriot Tadhg An Asna whose memory is commemorated by a monument at Clonakllty, was also a grandnephew on the maternal side, of O'Donovan Rossa. The late Mr. Kennedy was associated with the Irish Volunteers from the inception of that force, and was actively associated with the language movement in Cork in the pioneer days of the Gaelic League. Because of his views he was interned for a period at Cork Barracks shortly after the signing of the Treaty. Though subsequently offered a remunerative post as an engineer under the newly formed State, he declined, as he deemed its acceptance would not be compatible with his political beliefs. For his widow and family deep sympathy will be felt in their tragic bereavement.

The other clues I have is from a distant cousin who said his grandfather told him the Donovans lived at Blackrock.  A 2nd clue is with a John Donovan who owned at house and business at 35 Mary Street, Cork City in early 1900's and when my grandfather Brian was married in 1922 his adress was given as this Mary St address so there must have been some connection between John Donovan and Mary Anne Donovan Brian's mother one would think, then when John died in 1915 a funeral was held at South Parish Church but then he was taken to Lisgoold Cemetery even though 3 months earlier Johns wife had also died and she was buried at St Josephs Cemetery, so for John to be buried at Lisgoold I was thinking that may have been his native place, all very confusing with so many options. 

Whilst it would be nice to progress the Kennedy's further my main object is breaking through the Donovan puzzle so any help would be greatly appreciated.

Thank you

Phillip