Three year toddler speaking in sentences, but his grandparents and your friends have a difficult time understanding him. Does he have a speech disorder? Does he need speech therapy. How do you decide whether to treat or not?
First, what sounds does he have in words, phrases, and sentences? At three he should have the sounds p,m,h,w and he may have b,t,d,k,g. Okay, he is three. Some days he wants to talk sometimes not so much, that is the privilege of being three, right?
He may be developing quite normally. It is not unusual to have only those close to a three year old really understand all their utterances. however there are some signs he may need help. Does he get frustrated when people don’t understand him? Does he speak in short sentences? Do you and others understand most of what he says? If you are not sure ask your teachers at school or pediatrician or call your local speech pathologist.