Can spouses or close family members Witness POAs, Wills, Advance Directives?

Can spouses or close family members Witness POAs, Wills, Advance Directives?
Is it legally permitted for spouses and other close family members to sign as a Witness on a Durable POA, a Will, and or an Advance Directive in New Jersey, or must Witnesses be non family members for the above 3 items to be legally binding? Thank you.

inhertanceforaminor My sons father died i was the beneficiary on the policy.

inhertanceforaminor
My sons father died i was the beneficiary on the policy. We got divorced and his sister became power of attorney changed the beneficiary and will not give my child any money. What legal right does he have and is the life insurance policy a contract or part of the estate? Can I sue her for the money on behalf of my son ?