Turns out Hugh Lyle Black's [well a Hugh Black of Cloughfin anyways] mother may actually be Sarah, meaning Sarah Lyle is most likely his mother and not grandmother as I suggested.
According to GRONI, a Sarah Black, aged 78 died on 6 September 1874 at Cloughfin, her death was witnessed by a Hugh Black of Cloughfin. Thomas Black died aged 86 on 7 November 1879 at Cloughfin, witnessed by Hugh Black of Cloughfin.
As the Sarah Lyle I have was born around 1800 as her siblings were, her estimated year of birth, going by her death record (knowing full well sometimes they forget their real age), would have been 1796.
This also helps clarify why Hugh was called Hugh Lyle Black, for instead of just his middle name being his mother's maiden name, his forename and middle names both came from Sarah's fathers name.
As such I would amend the above short pedigree too:
Hugh Lyle Black
- Sarah Lyle & Thomas Black
--Hugh Lyle (c1759-1853) & Nancy McLean/Ann McNeill [was married twice]
---John Lyle & Mary Kenning, married 1740
----Robert Lyle, b. 1693 & Mary
Griffith's Valuation also only contains two Thomas Black's in Kilcronaghan, one in Mormeal and the other in Cloughfin. Meaning there can be no doubt this is the Thomas Black father of Hugh. Most likely they are both the same Thomas who simply had lands in both townlands. Looking at the PRONI valuations:
In 1881, Hugh Black officially took on Thomas Black's lease in Cloughfin.
In 1884, Samuel Black took over the Cloughfin lease from Hugh Black.
Between 1864-1883, an Alexander Black took on Thomas Black's lease in Mormeal. No year is pencilled in in the margin however. Though other entries I see for other people in the same dark blue ink are in the early 1880s.
Would safely say both Thomas' from Griffith's ar e the same and Alexander, Samuel and Hugh may all be brothers. Around 1884 must have been when Hugh moved from the area to Ballintemple.
[Edit:] Further confirmation of Thomas Black and Sarah being husband and wife from their headstone at Tobermore Presbyterian Church:
Erected by
Thomas Black
To the memory of his wife
Sarah Black,
Who departed this life 6th Sep.
1874 Aged 78 years.
Stone broken at this point