In 1440, King James of Scotland was 10 years old, and the power struggles around the throne were deadly.  The Douglases weren't, at the moment, as powerful as they had been, but would be stronger any minute, as the 16 year old 6th Earl of Douglas would indeed be getting older.  Unless somebody murdered him first!  There's an idea!  Were the 6th Earl and his little brother invited to Edinburgh, given a mock trial and beheaded?  Yes.  Yes, they were.  Was there a dinner first, at which their upcoming deaths were announced by a black bull's head being slammed on the table?  No, and no.  Was the child king there, sobbing and begging for their lives?  Nope.  Did George R.R. Martin know this famous story, and did it influence his Red Wedding?  Yes.  But that still doesn't make it true.