A man dies, he has no wife and no children but has the children of a full brother who is deceased. Shaikh Ibn Baz.

Question: A man dies, he has no wife and no children, but has the children of a full brother who is deceased. So do the male and female children of the brother inherit from their deceased uncle?

Answer: If the situation is as you have described then all of the inheritance goes to the sons of the full brother and not his daughters—this is by the ijmā’ (consensus) of the Muslims due to the statement of the Prophet: “Give the shares to those who are entitled to them, and what remains over goes to the nearest male heir.” Bukhari and Muslim. And that is because the daughters of the brother are not from those who are given prescribed shares (ahlul-furood) from the estate of the deceased and nor are they from those who are given non-prescribed shares (ahlul-‘asabah). Rather they are from those who receive a share when no one remains from ahlul-furood or ahlul-‘asabah—and this is by the consensus of the scholars. 

Majmoo’ Fatāwā Ibn Bāz 20/206

Note: In the case of female heirs, the inheritance stops at them (i.e. sisters, daughters, etc) and does not move on to their children as in the case with male heirs.

So the above is the inheritance for those who have a right to inherit in the Shariah. As for a legacy (wasiyyah), then a legacy of a maximum of 1/3 of one’s estate can be left to non-inheritors or a charitable cause.