There was only one family named Neill in Blackhead. They were Thomas Neill and Bridget Moorw who were married in 1851. Bridget is probably related to the other Moores in Blackhead, maybe a sibling of Thomas and John Moore.
Thomas Neill and Bridget Moore have at least five children between 1855 and 1865. However, after 1865 there is no evidence of the family.
For the Blackhead Family Tree of the Neill Family check out: The Blackhead Neill Family History