Technically you're not responsible for either. That having been said, a prenuptial agreement may be something you wish to consider, particularly if you have substantial assets to protect.
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Your asset would generally only be subject to possible seizure if he (1) owed arrears, (2) she got a judgment against him, and (3) you converted your assets to joint names. That said, a prenuptial agreement is the way to go. Schedule a consultation with a NYC Divorce lawyer for a full assessment.
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All other attorneys are correct that a Prenuptial is a great way to go. The point no one else mentioned but comes to my mind is whether it should be drawn by a New York lawyer or a New Jersey lawyer . So I would consider which state gives you a contact that would be more enforce3able in the state that you choose. As both a New Jersey and New York practicing attorney what effect having the laws of their respective state govern the agreement.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in NY so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.
Alternatively, you can simply keep all your assets separate except those that you want in a joint bank account or otherwise jointly. There is no risk to your separate assets unlike a theoretical or actual threat to the joint asset(s).
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