
You can only ask one yes/no question to one of the brothers. What should your question be to find the safe path?
This is one form of a well known logical puzzle known as ‘Knights and Knaves’. This particular format was used in the 1986 film Labyrinth.
The puzzle has many variations and in the future I will post one that is annoyingly more complex. For now, let's see what the answer should be for this one.