My daughter, Hayley, 18 months old, was diagnosed with CF due to reflux. Her condition started with reflux at about 2 months old, failure to gain weight, vomiting most feedings. We tried Zantac, switching formulas, nothing was working. They she began aspirating her formula into her lungs, which caused respiratory problems, she turned blue a few times and we went to the hospital. She was admitted and several tests were run, upper GI and a Broncoscopy, both of which confirmed severe reflux. My daughter was even on a ventialtor for about a week. She had a surgery called a Nissen Fundoplication (stomach wrap, if you google it you will get the scientific explanation). She now cannot vomit or burp even. But she still continued to have respiratory problems even after the surgery and recovery and that is when they did the sweat test and we got the CF diagnosis. From everything I have read acid reflux and reflux are VERY common in CFer's and in my opinion your cousin should have their child tested just to rule out CF because kids do so much better the earlier they are diagnosed!! Hopefully they are seeing a gastroentrologist (probably butchered that spelling!) that can help with the reflux and maybe even suggest the sweat test! Let me know if you have any other questions!!