Hello Len,
I am still looking for a thread through from my G.Grandfather Joseph QUILLIAM (1815 to 1883 in Patrick) to his birth father John QUILLIAM.

You suggested that Joseph may be the son of John Quilliam and Cath Chambers and to this end I have found his baptism on the Parish Registers, 19 Feb 1815 (illeg) son of the above, also his brother William 08 Nov 1818 as son of above.
As William was not shown as illeg. I thought that perhaps a later marriage of John and Cath may have taken place, but it does not seem so. In fact, Catherine now becomes my mystery woman - having married John Gell in 1811.
There are at least five John Q's in Patrick in the time frame but I have no way of knowing which one he is.
Do you have any further info that you can share that may identify him??
Many thanks,
Marjery