As explained on our "property Rights and Division" page here, in Nevada, premarital property is defined as separate property -- normally, only property accrued during the marriage is at issue in either a divorce or an annulment, and there are some distinctions between those two legal processes as to how property and other claims are assessed, as explained here and here.
As explained in detail on those pages, there is no specific time within which an annulment is allowed, but there are grounds to satisfy. You should have your son look at the posted materials, and then he should consult with a family law specialist to go over all of his options, costs, risks and benefits, probably as soon as possible.
Answered on Oct 27th, 2018 at 2:02 PM