There are many descendants of James Kirkwood & Jean Steill via Jean Kirkwood and John Anderson. Jean & John's son, John (born c.1796) married Isobel Shanks and were at Tannoch on the 1841 census.
John & Isabel's son, John (born c. 1816) was at Wester Waterhead on the 1851 census with his wife Catherine (John & Catherine are my 3x great grandparents).
One of John & Catherine's sons, Thomas, (who was born at Waterhead), ended up in Ardrossan, Ayrshire with his 10 children so I would guess there are descendants of James Kirkwood and Jean Steill in this area also.
With regards to my direct line, this ended up in Aberdeenshire when my great grandmother (who had Kirkwood as part of her name) moved to Peterhead when she married my great grandfather.
If you would like any more details let me know.