A neighbor, who is from NJ, told me...
Is the neighbor a (former?) NJ lawyer??? Is there anything, other than being from there that qualifies him to actually know what he is talking about??
The amount of misinformation that "everyone knows" is huge, and to be honest, just being from someplace doesn't mean squat.
I won't claim to know the exact NJ law. For that, you should seek out a NJ firearms LAWYER. However, in general the subject has come up before and has been discussed.
The general point is firearms being willed to someone whom the state says cannot have them. One case discussed was guns willed to a prohibited person. The same principle would apply to someone who does not meet state requirements for ownership (no FOID, etc).
What is generally done in that kind of case is that the firearms are held in trust, by the estate, until the prohibited person can legally possess them. The inheritor, if not legal to posess, can have them sold, or can give them away, through the executor of the estate, or they can even be held in trust for a future (legal) heir of the prohibited person.
I'm not a lawyer, but I have heard these things discussed. Naturally the specific situation and location determine what options are available.