Ambiguity in posseessive pronoun?

Question

"He reminds Maria of her ex." is translated as
"Il rappelle son ex à Maria."
What is the translation of "He reminds Maria of his ex."?In other words, how do we know whether the possessive pronoun refers to the subject or the indirect object?

Accepted Answer

Peter,  
In this particular French sentence and expression '…..rappelle son ex à …’ neither the gender of the 'owner', nor of the 'possession - the 'ex' - can be unambiguously identified without further context, as the noun 'ex' is invariable.
To clarify, this is a possessive adjective - in this case 'son' - which is doubly ambiguous here because it precedes an invariable noun that starts with a vowel -  ‘ex’.
The possessive adjectives themselves never identify the gender(s) of the ‘owner', although in many constructs and contexts it will be clear. 
The answer to knowing the meaning is context. The context would need to be known or provided in a longer description of the situation - this expression cannot provide that information in this simple format. If not, clarifying questions could/would be asked in a conversation. 
https://progress.lawlessfrench.com/revision/grammar/use-mon-ma-mes-ton-ta-tes-son-sa-ses-to-say-my-your-his-her-possessive-adjectives
 https://www.larousse.fr/dictionnaires/francais/ex/31911