My DNephew has a very sing-song voice and most of his speech is echolalic; he repeats much of what's said to him, and uses questions as his answers, always refers to himself in the third person ie if he wants a drink he'll say 'Jakey want a drink??'
I'm generally of the impression that this is part of normal development, especially as he's so young, but wondered what others thought? I don't see him that regularly, so haven't really been able to see him play much etc, but I don't think he has any other behaviours that cause concern (have been googling 
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Sorry if ANYTHING I've said is ignorant, I have no experience of this sort of thing