A stray late 18th Century Antrim family?

There is one family with a surname which could be a variant, albeit a remote one (some might say 'deviant') of McIlhagga. We know of this family because it appears in the 2% sample which has been preserved of the 1851 Census. The name is McIlligan. This name does not appear as a separate name or as a variation of another name in any standard dictionary of Irish or Scottish surnames and I think it is reasonable to think it has the same Gaelic origin as McIlhagga.

There is a 'nuclear family' at 14 Glenarm Altmore St in the townland and parish of Tickmanrevan. Tickmanrevan or Glenarm is in the barony of Upper Glenarm, County Antrim, on the northern coast. Robert is the head of the family, aged 23, a Blacksmith, born in County Antrim in 1828. His wife is Catherine, aged 21, a dressmaker, also born in County Antrim, in 1830. We can assume that Robert and Catherine were married in either 1849 or 1850 as they have a daughter aged one, hence born in 1850. Her name is Easter so we can assume that she was born in that season!

An added interest for us is the fact that in the same street, also recorded in the 1851 Census, in the house of Daniel and Rose Laverty, their daughter Mary and 'granddaughter' (sic) William McCloy aged 2, there is a Lodger whose name is recorded as 'Mary McIl...?' Daniel and his daughter Mary were both Labourers and Lodger Mary 'spinning wool'. I think it is highly likely that Mary was a widow and was the mother of Robert. Her name must have been partly obliterated on the census form subsequent to its being completed. There may of course have been several reasons why Mary chose to lodge near rather than with her son, new daughter-in-law and granddaughter. Presumably she wanted them to have the freedom to establish their own family, and she was 66. This meant that she became Robert's mother at the age of 43. Was he therefore the youngest child? The couple Mary was lodging with were more her own age. Daniel was 66 and Rose 55. It is interesting that Mary still worked, as a wool spinner, and could presumably come home to a meal prepared by Rose (listed without an occupation), rather than by her daughter-in-law who apparently also had to work. From a clan genealogy perspective Mary would have been born in 1785 and perhaps had been married to a clan male who had been born about 1780. Certainly this is a 'stray' clan family, if a clan family it be, for we know of no other family settled nearby, but, who knows, we may discover sometime how they fit into the wider picture.