About interrogative sentences

Hi,

We usually say:
"Do you know who you are?" No, we don't usually say this. It sounds rather odd. It sounds like a doctor talking to someone who has suffered a head injury.
"Who do you think you are?" Yes, this is commonly said, in cases where someone is doing things that are typical of another person. eg One of your friends starts giving you a lot of advice that you don't want, and you say to her, "Who do you think you are? My mother?"

Best wishes, Clive 

Hi Kevin,

Welcome to the Forum.

. . .  what I don't understand is, from a grammatical point of view, why we say:

"Do you know who he is?"
"Who do you think he is?"

rather than:

"Who do you know he is?" As you can see, all you have changed is the verb. The reason this is not correct is that we usually don't use the verb 'know' in this way. It's a question of meaning rather than of grammar. You can make grammatically correct sentences that are wrong because of the meaning, eg Who do you cook he is?

"Do you think who he is?" We don't use the verb 'think' in this way.

And by the way, which of the following sentence is standard?

"Who do you think is he going to invite home?"  This is not the correct way to form the question.
"Who do you think he is going to invite home?" This one is fine.

Best wishes, Clive

"Do you know who he is?" "Who do you think he is?"

The structures are as follows.

Indirect question derived from Who is he? embedded in the direct yes/no question Do you know?
(You know?) the answer to the question (who is he?).  >
(Do you know) the answer to the question (who he is)? >
Do you know who he is?  (Yes or no.)

Subordinate clause.  that omitted.
(You think ) that (he is someone). >
(You think) that (he is who) > 
(Who) (do you think) that (he is)?
Who do you think he is?   (Who is he? - in your opinion.)

CJ