At a time in my life when I hated the world and it seemed to reciprocate beyond all expectation, there was always one bright spot—my silly little brother Kevin. I had been the youngest of three kids for 12 years, but I never really felt the part. It got me no special treatment, and if anything I felt like the quintessential middle child from the beginning—and that made perfect sense when Kevin was born five days after my 12th birthday.

To our delight, Kevin was…