Legally, it is possible to disinherit a child in your state--that is, to not live anything to a child. That being the case, the terms of the will are enforceable, and everything should go to your daughter. The uncle's son can try to challenge the will if he believes--and believes he can show--that the will was obtained or procured improperly, such as through fraud, deception, "undue influence" (which is usually if the caregiver for a disabled or otherwise dependent person uses his role and influence to get a will changed or made), coercion, etc., or that the uncle was mentally incompetent at the time he made. But barring some fundamental problem like this with how the will was made, the son should not have grounds for a successful challenge.