My wife is a 1/3 owner of a condo Her daughter and then sun-in-law are the other two. Sadly. my wife daughter died in Feb of this year.

You write that your wife is a 1/3 owner.  Is she a joint tenant, a tenant in common, or perhaps a 1/3 owner of an entity which owns the property?  The answer to your question could be different depending on how  your wife owned her 1/3.   I will assume, since it is most likely, that your wife's daughter and son in law owned their interest as tenants by the entirety and your wife was a tenant in common.  IF so, her son in law now owns 2/3 of the property and your wife 1/3 as tenants in common.  If so, her son in law can't sell the property without her consent (unless there as an agreement allowing the majority owner to do so or he forges your wife's signature).  However, if he wants to sell and she does not, he may be able to get a court to partition the property, either dividing it up (if feasible) or dividing the proceeds of sale.