(A tangent off this speculative answer to a question about a sentence containing the words eidem suae.)
Does the apparently redundant phrase eidem suae ("to his/her/its own same") provide a way to indicate that the antecedent of suae is not the subject of the verb, as is normal for the reflexive pronoun in the dative case, but something else having a (different) reflexive relation to whatever follows suae?
A possible example, from the Apostolic Letter "Quod De Beatissima" by Pope Pius XII (1957):
Venerabilis Frater Constantinus Christianus Luna, Episcopus Zacapensis, a Nobis enixe postulavit, ut eidem suae dioecesi, noviter conditae nulloque Patrono adhuc concreditae, eandem Virginem a Fatima caelestem Patronam benigne eligere dignaremus.
This is a little beyond my current skill with Latin, but here's my attempt at a translation:
The venerable Brother Constantine Christian Luna, Bishop of Zacapa, has strenuously asked us, for his own newly founded diocese, as yet entrusted with no Patron, that we deem worthy to kindly choose Our Lady of Fatima as Patroness.
The subject of the relevant clause is the author, that is, the Pope. It would be silly if Luna asked the Pope to choose a Patroness for his own—the Pope's own—diocese, but that's what suae dioecesi would literally mean. So, I'm wondering if eidem suae is a way to relocate the antecedent of suae to where it makes sense and thus avoid a very clumsy circumlocution. And is this a common idiom?
If the same thing commonly occurs in another grammatical case, that would answer the question, too.