If Y is the brother of Z. W is the daughter of Z. O is the sister of Y. N is the brother of W then who is the uncle of N? 

Y

Note:

↑ or ↓ ⇒ Upward or downward line shown "generation gap" .

   =    ⇒ Double lines shown "relation b/w Husband & Wife"

   —   ⇒ single line shown "relation between them other than Husband & Wife".

   +   ⇒ Plus sign shown " Male".

   -   ⇒minus sign shown " Female".