Attracted to brother's wife

Joyce has been married for four years and they have three children. Her husband John comes from a united family and as a result, they regularly organise family meetings. John is particularly close to his younger brother Rob and they are always together.

But even though her husband and Rob are best friends, Joyce has never been close to Rob. Joyce only became close to Rob last year when she went back to school to do her Masters degree and found out that Rob was in the same class.