It occurred to me that the union of England and Scotland was substantially assisted by the fact in the initial union of crowns, it was the King of Scotland (James VI) who became King of England (as James I). This was barely acceptable in England, and the Scots didn't mind at all. That is, they accepted being ruled by the King of England because he was King of Scotland first.
But what if the bloodlines fell the other way.
First, was that possible? OTL, an English princess, Margaret Tudor, married into the House of Stuart. But AFAIK, no Scots princess ever married into a British royal house.
Second, supposing such a marriage had taken place, and the reigning King of England inherited the Crown of Scotland. Would the Scots accept this, or would they rebel against foreign domination?