Hi McJenn and welcome to Rootschat.
I see 30 people have looked at your post, but as yet no reply to it.
You will discover that most queries posted here on Rootscaht are replied to pretty swiftly, and there are some some very experienced, knowledgeable researchers on here, including Scottish experts.
That makes me think it has been very difficult for anybody to find anything to help you.
I see from your familysearch site you have found a great deal of interesting information and evidence about the family after their arrival in Canada.
A couple of questions:
1. Do you have any other evidence that the Kerr family came from Argyll?
You quote a ‘bio’ of Castle’s son as where you got this information.
This would have been written quite some time after their arrival in Canada.
I have found, as many others have, that family ‘facts’ can turn out to be a little different. Stories may be mis-remembered, or only partly remembered, or embroidered over time.
2. Was Castle the only child to have been born in Scotland? You have siblings as Margaret, Catherine and John. I think I saw the baptism of Catherine in 1804 in Canada on your site. what about Margaret and John?
If Castle was about 10 years old when they arrived in Canada, it’s likely they had other children in Scotland before going to Canada.
3. Have you found their arrival in Canada? I didn’t see any documentation to that fact on your site. What date do you think that was? It’s possible they didn’t go directly to Nova Scotia.
‘Castle’ is such an unusual name, one would think it was a family name passed down.
Have you seen, (and probably discounted!), the many hits that come up on familysearch for ‘Cathel Kerr’ in Assynt, Sutherland?
For example, Cathel Kerr baptised 10.12.1802, father Alexander Kerr, mother Christian McLellan.
This is a baptism of course, and it may be the child was born some time before this. The register may give more information.
Familysearch have the film for Assynt, number 7907468. It is digitised, but locked, so you have to visit a familysearch library to view it. It is just baptisms and marriages. No deaths at all. There is a search icon next to the locked film icon however, and you can search for all the Kerr families there. The name Cathel Kerr comes up several times, as sons of various Kerr male fathers. It was obviously a family name that was passed down.
The Assynt register only starts in 1798 according to the film information. It may have been a new church set up then. What they did before that I haven’t looked into, but I can’t see any earlier records either on familysearch or Scotlands people.
I know it’s a long way from Argyll, but it may be worth looking into in the absence of anything else.
Good luck!