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I checked the 1850 and 1860 U.S. Census.  The 1850 estimates him at 55 years old, and the 1860 estimates him at 60 years old.

But both list his place of birth as Scotland, and Sarah as Ireland.
I know during that period there was a lot of migration back and forth between Scotland and Ireland, so I imagine that he could have been born in either place...and met Sarah either in Ireland, or in Scotland....

I had a similar problem many years ago with a Great Great Grandfather on my mother's side in the U.S.   U.S. Census listed him as being born in one state, and the LDS records another.. I wasn't sure if it was the same person... eventually I found his grave stone, did a rubbing, and figured out they were the same individual. His family had migrated from one state to the next and back.. the census just recorded where he was living at the time, not where he was actually born...  That one took me years to resolve.

I know of two distant cousins that live not too far from the Cemetery where he is buried.  I'll see if one of them can do a rubbing.  But I fear we will need Parish records to find out for certain.

Yes,

The entire family migrated to the United States in 1849.  So there weren't any earlier census before 1841 and they left before the next census.  FamilySearch.org has in their index records of the births of several of their children, but I get no real information from that.

One report says William was born in Scotland, one in Ireland, and another in England.  Unfortunately I live in Trinidad & Tobago, so my resources are more limited than most.  I think the only way I'm going to find out anything will be from Parish records, because I don't believe they did anything notable.  In the U.S. they were William and his sons were coal miners. 

I did a search in the FindAGrave.com website for CLOSS in the Kirkoswald Parish Cemetery, but nothing turned up, so I don't think William's family was from there.