Uncle signed a paper in the US, gifting his portion of inheritance from mother’s house in Puerto Rico to sister. Legal?

Question

Grandmother died in 2013 without a will and she had seven children/heirs. The house remains in my grandmother’s name to this day, and my aunt moved in and took control of the house without the consensus of all the heirs.  
My aunt made a document for my uncle to sign in the U.S. in December 2022, which stated he was gifting his portion to his sister. It was NOT notarized, but it has a copy of his ID on the document along with his Social Security number.  
He was in a rush when he signed the document and didn’t realize it said he was basically donating his share to the sister. He says he was in a rush, and didn’t realize the document said he was gifting to her, because he was under the impression she wanted to pay him for his share. 
1.) Is this document that was signed in the US legal/valid in Puerto Rico? 
2.) Is he allowed to recant this document? 
3.) Is he allowed to gift his portion to one sibling or must it be distributed amongst the remaining heirs?

Rafael Pagan-Colon · Answer

There are three ways in which an heir can transfer his/her hereditary rights to another: by ceding said rights to another, by donating the rights or by repudiating his/her inheritance. The first two must be done by subscribing a deed (escritura) before a notary, with both the donator and the receiver subscribing (the latter, to accept the grant). A donation or cesion may be granted to whomever the donator wishes. In the case of a repudiation, it may be done either by subscribing a deed or by sworn motion before a court of law; and the inheritance share is distributed among the remaining heirs. 
     Documents notarized in the state must first be legalized by that state's State Department or whichever state agency certifies a notary public's commission in that state. Even so, the document must clearly identify the real estate property whose hereditary interest is being transferred; else it's null and void. The Property Registry in Puerto Rico will not accept a document that does not identify the registry number (# finca) and the Center for Municipal Incomes Collection ("CRIM") property identification number (# catastro) of the real estate property. 
     Regarding your uncle, one would question what he thought he was signing, if he "was not aware" that he was signing his inheritance away. Regarding your aunt, if she has taken possession of the real estate which is evidently an inheritance community property, the remaining heirs can (1) notify her in writing that she must pay rent on while living the property (rent's due on hereditary properties are prospective, not retroactive); (2) negotiate with your aunt to reach a fair, amicable distribution of the inheritance; or (3) go before a court of law to demand by lawsuit that your grandmother's estate is distributed among the heirs.

Q: Uncle signed a paper in the US, gifting his portion of inheritance from mother’s house in Puerto Rico to sister. Legal?