SIR ROBERT KEITH, the eldest surviving son, succeeded his father before the end of 1410.{Frasers of Philorth, i. 81. .. married the heiress of Troup, whose name has not been ascertained, with whom he got that barony.{Douglas’s Peerage.]

By the first marriage be had:—

6. Christian, married to Thomas Monypenny.{Robertson’s Index, 141, 60.]

Generation Eight
http://www.robertsewell.ca/monypenny.html
Thomas Monypenny of Pitmilly
Died in 1427

Thomas married Christian Keith, a daughter of Sir Robert Keith, an ancestor of the Earls Marischal, and they had two sons:

1. John Monypenny
2. Sir William Monypenny who married in 1410 to Marjorie Arbuthnott, daughter of Philip Arbuthnott and they had, with other issue, a son ….

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References

1. https://www.douglashistory.co.uk/famgen/getperson.php?personID=I116...
2. https://www.stirnet.com/genie/data/british/mm4fz/monypenny01.php
3. https://our-royal-titled-noble-and-commoner-ancestors.com/p4798.htm... cites
   1. [S11649] Clan MacFarlane & Associated Clans Genealogy. < link >