Ballymena town: a Minnie problem

The final half a dozen baptisms at St. Patrick's, Kirkinriola, are all from the town of Ballymena itself, three from Queen Street, one from Patrick Place, one from Ness Street and one from North Street. They cover the period 1887 to 1911 so perhaps we can relate them to the 1901 and 1911 Censuses and even to the Ulster Covenant of 1912. The 1901 Census shows a family at 67 Queen Street: Robert and Margaret McIlhagga with children Lizzie (18), Minnie (17), Robert James (16), John (14), Samuel (10), Andrew (5) and Joseph (1).

Now here is our first problem. Not that I have the baptism of Joseph on 16 Jan 1900 (born 31 Oct 1899), to Robert (Labourer) and Margaret, but that I also have the baptism of a Minnie, daughter of Margaret McIlhagga of Queen Street (no number), Harryville, a Millworker by (Rev) J.W. Murrey, Deane. Now at this baptism only one parent is named, but the record doesn't say 'illegitimate', so it could be the family at 67 Queen Street, except that Minnie's dates are not consistent with the Census. The Census implies that Minnie was born about 1884 and the baptism record says born 8 March 1887 and baptised 30 March 1887. However, there is no other Minnie in 1901 and none at all in 1911 or 1912. Presumably by 1911 she had a married name.  I have no Minnie who fits the case in my marriage records and no other 'suitable' Minnie in my birth records. As Minnie age 17 at 67 Queen Street in 1911 wasn't an eldest child I must assume she was born in wedlock. So was there one Minnie and one Margaret or were there two Minnies and two Margarets? I am baffled.

The Kirkinriola records are as follows:

Baptism, 30 Mar 1887 (born 8 Mar 1887):
Minnie, daughter of Margaret McIlhagga, Queen Street, Harryville, Millworker, J.W. Murrey, Deane.


Baptism, 16 Jan 1900 (born 31 Oct 1899):
Joseph, son of Robert and Margaret McIlhagga, Queen Street, Ballymena, Labourer.

I have a further baptism on 18 December 1895 (born 1 October 1895) of Mary to John and Mary McIlhagga of 97 Queen Street, Ballymena, Labourer. The only couple who might 'fit' this record is I think John McIlhagga who married Mary Sloan on 5 January 1894 at Ballyclug Church of Ireland, Ballymena. He was to become a Railway Carter. According to the 1911 Census they had three children, all of whom died in infancy, and Mary, baptised in 1895, could well have been one of them. I have discussed this couple before and I think that John's father, also John, could well have been a son of James McIlhagga who married Jane Middleton.