just rereading through everything again .
so
Charles Moor Birth 04 Dec 1871 Donegal, Ireland Father John Moor Mother's Isabella Elliott . church hill donegal .
Charles Moor Letterkenny born 1871 Volume 17 Page 188
you can buy the correct birth 1871 from same website you bought other ones just make sure you put fathers first name in as john in advanced box , details should match up to info above .
this would seem to fit now from charles moore,s marriage saying fathers name john and his first two children named john and isabella .
on web site theres only the one birth to father john so it would seem to be correct .

https://www.census.nationalarchives.i...htown/1187111/
might well be his dad and witness-sister mary