I think you are correct that there are 2 Daniel Hegartys in Brockaghboy very close in age.
1) Daniel Higgerty/Hegarty born 14 Mar.1865 (Garvagh district)- son of Michael Higgerty & Mary Anne McNichol.
Michael Hegarty (d.16 Apr.1892) mentions 'wife' and called son Daniel his 'only child.'
2) Daniel Hegarty born 1 Feb.1867 Brockaghboy- son of Patrick Hegarty & Mary Ann Dillon.
I have michael's will and date he died but not his birth date or marriage date and I have no BDM for mary ann mc nicholl.
If Michael and Mary Ann were married in a Catholic ceremony before 1864 (and since son Daniel was born in March 1865 this is not unlikely) then there will be only a church record of the event (civil registration of Catholic marriages started in 1864).
Civil registration index shows death for Michael Hegarty (age 60) Apr./June 1892 Coleraine registration district volume 1 page 395.
I searched the index for Mary Ann's death (between 1901/1911) but couldn't find a likely one in Coleraine district- perhaps she went to Derry with Daniel and died there?
Do you have the details of all of Daniel and Bridget Jane's children? If not I might have some of their births.