The only direct link we have between John and the rest of the Ballyneill Harbisons, and William, is the death notice for his son Henry, in the 1885 Belfast Newsletter.
HARBISON—July 6. Henry, third son of the late John Harbison, Ballyneil, uncle to the Very Rev. Henry Harbison C.S.S.R., Dundalk. Funeral will leave for the family burying ground, loop, this day (Wednesday), the 8th, at 121 o'clock. Friends will accept this the only intimation R.I.P.The link was formed by two Henries; Henry, John's son, died in 1885; Henry the Redemptorist was the son of William Harbison, b. 1780. If John was his uncle, he was William's brother. There are two records of a John Harbison acting as godfather in Ballinderry in 1828 and 1829. And there is this entry in the 1831 census for Ballyneill More.