I noticed some DNA links on a different Stuart profile and was curious if those were legitimate since usually they are not. This particular John "Bushyhead" Stuart (nb. his father preferred the Steuart spelling) is the ancestor who connects them to the Royal Stewarts through Sir Walter of Kincardine, a natural son of Alexander Earl of Buchan. If valid this connects him to both Bigod and de Clare surety barons. Walter's descendants at Kincardine I can't find documented in the Scots Peerage, which doesn't mention this detail in the Earl of Buchan bio and I couldn't find them in MCA either.
I reviewed the line and I didn't see any obvious problems, other than the sources are not very high quality. I tagged him as questionable and hope that one of the MCA or Scottish clan experts will review his ancestry further.