Robert Scott-Moncrief and Anna Wellwood did have a son Robert Scott-Moncrief, who did succeed his father in the estate. However, he changed his name to Scott-Wellwood, and then died without issue (no marriage, no children). This is according to the genealogy book "House of Moncrieff", pages 128-129, as found here:
https://www.familysearch.org/library/books/records/default?search=m...=
Or go to familysearch.org, select search, then books, then search term "moncrieffe". Should be the first on the list.
