MTK, please google the following cases (or check out the article by Siegler and Talel in the 11/03/2004 issue of the NY Law Journal):

Thwaites House Owners Corp. v. Vega
Wiesz v. 233 East 69th Owners Corp.
445/86 Owners Corp. v. Haydon

All of these cases ruled that "Lessee AND" was *not* ambiguous and *did* require concurrent occupancy by the shareholder. If you are aware of more recent cases that have ruled otherwise (the anomalous Barbizon case predates these), please let me know.

It's not unreasonable to leave the relative alone, but the issue is that it may affect your ability to collect sublet fees on other apartments. That's a question for your co-op attorney. I'm not a lawyer and am not sure of the answer.

JG: I agree that making an effort to regulate roommates of subtenants in co-ops - or roommates of anyone in a condo - is replete with thorny problems and is a bad idea. The Roommate Law may apply with 100% certainty only to rental buildings and shareholders in a co-op, but it seems very likely that it would be extended to subtenants and condos if challenged.