John was 39-3=<<39-3=36>>36 years old 3 years ago
So that means in 6 years James will be 36/2=<<36/2=18>>18 years old
So right now James is 18-6=<<18-6=12>>12 years old
So James's older brother is 12+4=<<12+4=16>>16 years old
#### 16