Thought I'd write as I have GEORGE ancestors from Kenwyn, Cornwall and I was born in Pittsburgh.
There is a wealth of information available online to help in the search for Nicholas's family.I suppose you're aware that Nicholas George's 1912 arrival is found at the Ellis Island site http://www.ellisislandrecords.orghttp://www.ellisislandrecords.orgIt is misindexed under Nichols George.He was 55 years old and headed to his wife's in Braddock, Pennsylvania.He was born in Perranwell and had last stayed at his brother Edward's in Greenwith, Perranwell.He had previously been in the US 1900-1910 which fits with your information on emigration date and birthplace.He was a boilermaker.
Your family is living in Greenwith Common minus your grandfather, Nicholas.I guess he was away working somewhere else at that time.The daughter, Jessie was said to have been born in Pennsylvania so it appears they were in Pennsylvania for some period in the 1880's (or at least the mother Jane Ann was!)And that could explain why Jessie was already a US citizen.Your father was 4 and there was a 1 year old Nicholas Gerald in the household in 1891.
The 1871 Cornish census is online at http://www.kindredkonnections.comhttp://www.kindredkonnections.comThere is a 15 year old Nicholas living in Perranarworthal district 6 schedule 003.He is listed as a labourer and a son although for some reason the head of the household is not given on this page.Edward is also listed as a son with the same district and schedule number and no head of household.The head though at this location is a Grace GEORGE, 56, widowed and born in Gwennap.Gwennap is even nearer to my GEORGE ancestors.So it appears that your greatgrandfather was dead by 1871.Grace though appears in the 1881 and 1891 censuses.
Now what I think you'd be really interested in is the 1861 census.This is available at a pay per view site http://www.familyhistoryonline.nethttp://www.familyhistoryonline.netYou can search the index for free.There were 7 Nicholas GEORGEs in the 1861 Cornwall census.If you pay for these seven, then you can get the birthplace and ages and then look for the household of the Nicholas of the right age born in Perranworthal.Hopefully your greatgrandfather would still be alive and you'll get the information you need at a reasonable cost.
Eventually the Cornish online census project plans to have the 1861 census online as well as the 1841 and 1891.So if you're patient you could also wait for that.Check the site I mentioned before and maybe the 1841 is online with Grace already married to your greatgrandfather.