Illi has the same form for the 3 genders when it's dative, but here, it's nominative (=subject), so it's a male "they".
Male they: illi, (ils in French)
Female they: illae, (ellas in Spanish)
Neutral they: illa.
(note: it's only the plural "they", not the singular they referring in English to an unknown gender, as it's non existent in Latin).
It's very interesting. I've found ii = ei,
but not illi = ii or illi = ei.
Do you have a source?
ei = ii = eeis (archaic)
Found in the second table here:
Plural nominative of "ille" (ille is masculin).
Ille: that, he.
Illi: masculine (plural): those, they.
- illos : accusative masculine plural
- illas : accusative feminine plural
- illis : dative/ablative masculine/feminine/neuter plural
Here the complete declension:
It is quite difficult for me to explain it in English (which is not my mothertongue), but I will try.
There are three demonstrative pronouns in Latin:
- hic, haec, hoc (plural: hi, hae, haec) : this (here) => someboby/something near
- iste, ista, istud (plural: isti, istae, ista) : that (there) => someboby/something a bit further
- ille, illa, illud (plural: illi, illae, illa) : that (over there) => someboby/something far away
However, the pronoun "is, ea, id (plural: ei/ii, eae, ea)", which is most of the time translated with a personal pronoun (he, she, it), can also be translated with a demonstrative pronoun.
Duos oratores adsunt. Eos audio. Hic malus est, ille optimus est.
There are two orators. I hear them (or eventually: these ones). This one is bad, that one is very good.