Here's a brief outline of the family. They lived on the Co.Londonderry/Co.Antrim border so some records indicate Coleraine district and others Ballymoney (Portrush comes under Ballymoney district). Think I can get a bit more which I'll post later.
William McKay (c1856 Co.Antrim-aft.1911) m.(12 Dec.1877 Coleraine district) Catherine Loughrey (c1857 Co.Derry-aft.1911)
www.census.nationalarchives.ie/pages/1901/Antrim/Portrush_Rural/Crighuller/931933 www.census.nationalarchives.ie/pages/1911/Londonderry/Ballylagan/Corrstown/595446 (8 children/6 living)
? Death: William McKay, age 52, 12 Apr.1914, Portrush sub-dist., Ballymoney dist.
1.
Ellen McKay (18 Jan.1879 Portrush sub-dist.) m. John McDowell
Birth:
https://familysearch.org/ark:/61903/1:1:FPQY-JRC2.
Thomas McKay (12 Oct.1880 Portrush sub-dist.-aft.1911)
Birth: Son born 1880 Ballymoney district:
https://familysearch.org/ark:/61903/1:1:FP7W-2J53.
Mary McKay (26 June 1883 Portrush sub-dist.)
Birth: Mary McKey born 26 June 1883 Ballymoney dist. (mother- Loughrey)
4.
Sarah or Eliza Jane McKay (c1886 Coleraine sub-dist.-aft.1901)
Birth: Eliza Jane McKay born 8 July 1885 Coleraine district (mother- Loughrey)
5.
Annie McKay (6 Aug.1889 Portrush sub-dist.-aft.1901)
Birth: Annie McKay born 6 Aug.1889 Ballymoney district (mother Loughrey)
6.
Fanny McKay (6 Apr.1891 Portrush sub-dist.-23 Feb.1900 Portrush sib-dist.)
Birth: Fanny McKay born 6 Apr.1891 Ballymoney district (mother Loughrey)
Death: (Jan/Mar.1900):
https://familysearch.org/ark:/61903/1:1:FT6Z-HWY7.
Samuel J. McKay (8 Jan.1893 Portrush sub-dist.-aft.1911)
Birth: male McKay born 8 Jan.1893 Ballymoney district (mother Loughrey)
8.
William Alexander McKay (15 Feb.1895 Portrush sub-dist.-aft.1911)
Birth Alexander McKay born 15 Feb.1895 Ballymoney district (mother Loughrey)