I've just come in on the end of this thread after trying to unravel the Blacks for quite a while.
I think I might have just worked it out!

My line comes from the George Black(cabinet maker) son of widow Ann on the 1851 census.
His father according to his marriage certificate (which I have a copy of) is James Black , That means that his parents were probably James and Ann (Corkill). A James was buried in 1836 which would account for his not being on the 1841 & 51 census returns.
On the 1851 census Ann (widow) is living with George and her other son James is next door,
with his family .
Their father's parents from what I can make out were Robert Black and Catherine Moore,
who also had Richard who married June Garret. Their son was called James also and he married Jessie Mather.
To add to the confusion George (son of Ann Corkill) went on to marry a Charlotte Mather
(a sister of Jessie perhaps?)daughter of Alexander, which may account for the middle name of quite a few Black offspring.
I hope this will help somebody out. It does sound confusing but if you draw it out it all becomes clear(?!)