"The gods kill their enemies."
Translation:Dei hostes eorum interficiunt.
Right. Lucky people, who have the gods killing off their enemies for them! (The gods' own enemies are hostes suos.)
NON-reflexive possessives for the 3rd person (his, her, its; their) are the genitive forms of is, ea, id: his/her/its: eius their (masc/neuter): eorum their (fem): earum
So, if I carry his books: Libros eius porto. He carries their (the girls') books: Libros earum portat.
But, in 3rd person reflexive situations, there's the possessive adjective, suus, sua, suum.
He's carrying his (own) books: Libros suos portat. (And so forth)
okay, so in your examples:
"Libros earum portat" is the use of a NON-reflexive (possessive) pronoun
"Libros suos portat." is the use of a reflexive (possessive) pronoun, because it refers back to the subject.
Is that correct?
And it looks like English doesn't make this distinction between reflexive and non-reflexive POSSESSIVE pronouns. So this is a new skill to learn in Latin.
Yes--just so. Latin allows you to specify whether the possessive refers to the subject or not. English doesn't. It is one way Latin is better than English. On the other hand, Latin doesn't have enough verbs, so it compounds verbs and uses them to mean a whole bunch of things. Which makes translating Latin (especially without context) really difficult.
I did some research and found out that "genitive forms of ejus, eorum, earum are often used as possessive for non-reflexive third person".
It helps to think of "ejus/eorum/earum" not as "his/her/their" but "of him/of her/of them".
Caesar, Bello Gallico I, 11, 1 : "eorumque agros populabantur" => "and they ravaged the fields of them" (=their fields)