I had to find an ENT for my daughter when she was 8 months old (she is now almost 15 months). I, too asked the mom's on MamaSource, and I specified that I wanted to know WHY their doctor was great. Bedside manner was not my priority- I wanted the BEST doctor, not the nicest. It turns out we got both! I got multiple solid, detailed referals to Dr. Neelesh Mehendale (Neal-ish Muh-HEN-duh-lay) at the Centenial Medical Center in Frisco. We drove way out of our way to go to him & we have been very happy. He is very thorough and explains everything to you in layman's terms. He is also very good with kids. Our daughter had surgery to have tubes put in her ears and he & his staff made it very easy on all of us. I feel confident he would be very thorough with your nephew. Check the rest of my responses/requests to read the other mom's referals if you like.
Good luck!
Suzi