excessive vomiting

Hello,

My nephew who is 18month now vomits excessivly.it has been that way since birth.  he vomits anytime but mostly after eating. we have gone to the doctor and they say there is nothing wrong with him and diagnoise him with GERD.  we don't over feed him at all he eat small meal every two to three hours and we make sure he sits up for a least an hour after eating but he still vomits and he becomes very tired after a vomiting episode. I just found out last week that his uncle who is about 30+ and the uncle father has the same issue.  they have tried everthing but they still vomit. My question is there a name for this kind of disease and what is the best way to help my nephew?