I have been playing with the Internet sites again! I read in the latest issue of the magazine of the Glasgow and West of Scotland Family History Society that sometimes a missing offspring can be found in FamilySearch.org by putting in to the search boxes only the parents names. I haven't done this yet, but I have tried a number of different ploys.
I put in McElhago as mother and got two people I knew about. I put in McElhago as father and got three people I already knew about. I put McElhago in to the father's first name and came up with a family McEllego in Madera, California in the 1910 US Federal Census. I haven't tried to research them yet. McElhago in the mother's first name didn't produce anything. Neither did McIlhaga nor McIlhagger anywhere. McIlhagga as a first name produced four people only one of whom I knew. He was William McIlhagga Boyd in the Scotland Births and Baptisms Index. He was born 24 Mar 1873 in Greenock, Renfrew, to James Boyd and Jane McIlhagga.
The other three had surnames I recognised from families that had married a McIlhagga, though as yet I don't know exactly where they fit into those families. They all come from the Ireland Civil Registration Indexes as follows:
Jane McIlhagga Rush, born Jan-Mar 1920, Belfast;
Agnes McIlhagga Clarke, born Jul-Sep 1910, Ballymoney;
George McIlhagga Whiteside, born Oct-Dec 1908, Ballymena.
Finally I put in a 'wild-card' version of our name, McIlhag* and got two more middle names, again with recognisable surnames, though again I'm not quite sure where each fits into a family. They are:
John McIlhaggard Wilson, born 1895, died Jan-Mar 1896, Belfast;
Elizabeth McIlhaggs McPhee, from the Ontario Births, born 21 August 1910 in Nepeau, Carleton, Ontario, to parents John Thomas McPhee and Elizabeth McNinn.
Another time I'll tell you what happened when I put McElhag* into the search boxes.