My 26 month old grandson talks a lot, is a wonderful happy toddler.
BUT he refuses to answer questions; specifically yes/no questions, like do you want milk?
Nothing back. But a few secs later he will say "i have milk?". He speaks very well, and is otherwise a very normal beautiful child. I don't know if this is relevant, but he was born at 29 weeks but has no obvious deficits. This is his only trial, really. Any thoughts?

Sounds like normal to me. Just give him 14 years. He won't even ask for the milk then.

In 14 years, not only will he not ask for milk, he will drink it straight out of the container.

Your grandson sounds normal. Turn the tables on him. YOU ask HIM questions that he can say yes or no to -- or even give one- or two-word answers.

He could be stuborn. Most 6 year olds I babysit won't either.

Don't worry about this... its just a stage but just in case.. if it gets worse than go to a doctor.. but most likely it will go away...