Initially, please consider this response to your inquiry general and preliminary guidance. You should consult with an experienced real estate lawyer who will need to review the deeds and other transfer documents to more properly advise you.
Based on the information you presented in your inquiry, upon your parents divorce, the property was legally held by your mother and father as joint tenants (as opposed to tenancy by the entireties during their marriage). Their new spouses would have had no interest in the property. Thus, either party would have been legally within their rights to sell or transfer their 1/2 interest in the property. To the extent it appears that upon transfer of title to your uncle both of your parents signed the deed, again, based on the information you provided, regardless of whether a lawyer or a notary prepared it, the transfer of title sounds like it was a legal transfer and your chances of declaring the deed to your uncle as null and void would not be likely.
Again, in order to properly advise you, a lawyer would need to review all of the relevant documents and I would suggest you do so.
Marla D. Sones
Answered on Apr 03rd, 2012 at 11:42 AM