Hi David,
I have also done a Keig family tree, going back as far as William Keig and Elinor Quirke. Like you I have found it impossible to find William's parents. My father had a tree drawn up many years ago which showed that William's parents were Thomas Keig and Catherine Cornish however no evidence was provided to prove this. Despite extensive searching, William's parents remain elusive, much to my frustration!
I would love to correspond with you regarding the Keig family, either through this forum or am happy to provide my email address.
I would be interested to know where you fit into the family ... I am the great granddaughter of Thomas Keig and Annie McGuire and the granddaughter of George Keig and Selina Taggart.
Regards, Linda.