At least one pedigree published by MyHeritage claims that William Keith, indweller in Edinburgh, is the son of William Keith, Earl Marischal, and his wife Lady Elizabeth Seaton. This is wrong.
MyHeritage
https://www.myheritage.com/matchingresult-c0785135006cfb2bc48bda897...
William Keith, Earl Marischal
Lady Elizabeth Seton
The Earl and his wife did have an only son named William Keith, Lord Keith, whose baptism was registered at Tranent in East Lothian on 11 August 1638, but he is reported to have died in infancy. A date and place of death has not been identified for William Keith, Lord Keith, but the fact that his father died without surviving issue is confirmed by the additional fact that he was succeeded as Earl Marischal by his brother George.
The Scots Peerage VI: 60
https://archive.org/details/scotspeeragefoun06pauluoft/page/60/mode...
William, Lord Keith
Unless objections are made, or alternative evidence is brought forward, I propose to disconnect William Keith, indweller in Edinburgh, from the family tree of William Keith, Earl Marischall and his wife Lady Elizabeth Seton.
