1) A person may will his or her assets to anyone he or she wants--there is NO obligation to leave anything to family members apart from the fact that you cannot completely disinherit a surviving (still alive when you die) spouse in Nevada--a surviving spouse can basically get 50% of your community (marital) property. But other than not being able to completely disinherit a surviving spouse, you don't have to give anyone anything: you can give family members nothing or relatively little, while leaving the rest to others.2) Yes, you can have a clause that in the event of an unsuccesful challenge, the person(s) challenging will receiving nothing instead of what you left them. (Obviously, if the successsfully challenged the will and had it set aside, such as for lack of mental capacity or coercion/duress, then it doesn't matter what the will says.)