Denis Donovan and Mary Donovan married but the record not to hand.
It seems that this Denis was also known as Denis Charles.  We will see below on comparing his name Denis Donovan on the Civil Death Register and the inscription on the headstone as Denis Charles that it is one and the same person who died on 6 October 1867.
 

Children born in Keamore (Keymore), Leap, Co. Cork and baptised in Kilmacabea RC Parish on dates shown:-

Honora Donovan, 25 April 1852; Sponsors: Daniel Casey, Ellen Hotohan

Julia Donovan, c 1853.  record not located

Mary Donovan, 13 July 1856; Sponsors: Timothy Donovan, Ellen Donovan

Eliza Donovan, 14 July 1859; Sponsors: Timothy Sullivan, Mary Connor

James Donovan, 12 Dec 1860; Sponsors: Jerry Donovan, Catherine Donovan

Denis Donovan, 1 May 1963; Sponsors: James Collins, Norry Callaghan

Death record of Denis Donovan:
From the Civil Death Register we see that Denis Donovan of Keymore, a farmer, and a widower died on 6 October 1867.  He was aged 48 years. The certified cause of death was "Compound fracture legand fever  Three Month(s)" Present at his death and the Informant to the Civil Registrar on 11 October 1867 was Julia Donovan of Keymore.

Wording on headstone in Kilmacabea graveyard:

SACRED
TO THE MEMORY OF
DENIS CHARLES DONOVAN
WHO DIED AT KEYMORE
OCT 6TH 1867
AGED 48 YEARS

Have pity on me least of my friendsJob 19c  21vs
In life we loved him in death we pray for him
May Jesus crusified have mercy on him
Mary Immaculate pray for him
may he rest in peace amen

Blessed are the dead who die in the Lord Rev. XIV. 13