“I am confused that I know George VI had 5 siblings. That excludes me from possible worlds where George VI had 3 siblings, or 7 siblings, or no siblings. Each bit of evidence in my mind excludes me from half of all possible worlds. Why do I know so much?”
A better analogy would be:
“I am confused that I know George VI had 5 siblings. That excludes me from possible worlds where George VI had 3 siblings, or 7 siblings, or no siblings. Each bit of evidence in my mind excludes me from half of all possible worlds. Why do I know so much?”