He died and left behind a wife and nephews and nieces

If a man
dies and leaves behind a wife and nephews and nieces, and there are no other
heirs apart from these, then the wife gets one-quarter because there are no
children. The sons of his brothers get the rest by virtue of being male
relatives on the father’s side, and it should be divided equally among them.
The sons of his sister and the daughters of his brothers do not get
anything, because they are not among the male relatives on the father’s
side.  

Allaah says
concerning the inheritance of wives (interpretation of the meaning): 

“In
that which you leave, their (your wives) share is a fourth if you leave no
child”

[al-Nisa’
4:12]

And the
Prophet (peace and blessings of Allaah be upon him) said:  “Give the
shares of inheritance to those who are entitled to them, and whatever is
left goes to the closest male relative.” Narrated by al-Bukhaari (6732) and
Muslim (1615). This indicates that male relatives on the father’s side may
be entitled to inheritance, and that the closer relatives take precedence
over those who are more distantly related, and they inherit after the shares
of inheritance have been allocated, if anything is left for them. 

What is
meant by shares of inheritance is those that are stipulated such as one half
or one quarter or one eighth. 

And Allaah knows
best.