1. Here is a man who wants to see you.
2. Here is a man wants to see you.
3. There are two boys who want to play tennis.
4. There are two boys want to play tennis.
(Can we omit 'who' as in #2 and #4? Are they all correct?)
2 answers
no you cannot take out the who in any sentence. Read them out loud to your self. The second ones just do not sound correct and that is because they are not. Proper English will keep who in both sentences.
Anonymous is correct. The word "who" is necessary because it's the subject of the word "want(s)."