Legal Question in Family Law in California

Your spouse is only entitled to share in the 401k to the extent of earnings during the marriage. Given your circumstances, however, a prenup that waives all interest in the 401k might be a very reasonable thing to do, particularly if you will be funding any other investments during the marriage. A prenup at this stage in your life is probably a good idea anyway, even if it just is an agreement on what separate property is being brought to the marriage, so neither of you has to go back and prove or fight about who had what when you got married. At a minimum, I would suggest that you put a copy of your last 401k statement before the wedding in a very safe place, and if possible change where the new money is invested after the wedding so that there are separate pre and post marriage funds to make it easy to track and hard to argue about.