[doesnotexist]

At first I thought there was a bug in experiment 2b he writes that the sample space should be:

{'BB/?b', 'BB/b?', 'BG/b?', 'GB/?b'}

Because he describes the event as "He is observed at a time when he is accompanied by one of his children, chosen at random."

I thought he also needed to include two more cases:

{'BB/?b', 'BB/b?', 'BG/b?', 'GB/?b', 'GB/g?', 'BG/?g'}

Which again gives us 1/3 probability of both being boys.

but I guess the part that comes after the '/' indicates the observation event.