Thanks for your query Keith, but such a theory isn't accepted by Clan Munro USA. I would refer to their research in the link above and below. Their report considers multiple Roberts, but they still reject any identification of William's father unless additional evidence is found.
"Not only is there no proof that William was the son of Robert of Aldie, there happens to be two people named Robert of Aldie who could possibly have been his father. Some researchers say William was the son of Robert Munro of Aldie b. about 1566 who married Isobel McKenzie, but most Munro genealogists have settled on Robert Munro of Aldie b. 1590 and married Elizxabeth Johnson. Other researchers erroneously say William was a son of Robert Munro XIV of Foulis."
It should be noted that Robert (Munro) Munro XXth of Foulis (abt.1595-1633) had no male children.
If you're trying to connect William of Lexington to the Munros of Foulis, this would seem difficult to do based on the reported Y-DNA data linked above. The reasonable conclusion is that he was not from the Foulis Munros.
I hope this information helps,