Sir Francis Stewart (later 5th Earl of Bothwell), the legitimate son of Lord John Stewart, aka Lord Darnley, is mentioned at least twice as a reversionary heir of one of more children of Robert Stewart, 1st Earl of Orkney, in vol. 1 of _Diplomatarium Orcadense Et Hialtlandense_ (pp. 173, 188): https://books.google.com/books?id=AhchAAAAIAAJ&pg=PA235&dq=1615+Orkney+walls&hl=en&sa=X&ved=0ahUKEwjgxvm2op7NAhVCeCYKHevfCjM4ChDoAQgoMAI#v=onepage&q=francis&f=false https://books.google.com/books?id=AhchAAAAIAAJ&pg=PA235&dq=1615+Orkney+walls&hl=en&sa=X&ved=0ahUKEwjgxvm2op7NAhVCeCYKHevfCjM4ChDoAQgoMAI#v=onepage&q=francis&f=false