I would love to hear from anyone who can definitely prove their connection to this couple. I have got lots of suppositions about descendants but cannot prove any of them.
About 1970 my father drew up a family tree showing that James Allanach (also known as Stuart) who married Isabel Rennie was the son of Duncan and Sophia. This family tree was widely circulated in England and USA and it is often quoted. However, we have never been able to prove the connection subsequently as we became aware that there were several Allanach families in Strathdon at the time and the birth/christening records are not complete. The closest we have come to corroboration is a branch of the Allanach's in California who have a family bible showing Duncan & Sophia as head of the family.
Would love to exchange information by direct email.