„Ei”. That is the genitive-dative form of the pronoun „ea”.
Do not confuse it with the nominative-accusative form „ei” (meaning "they")
If ei is genitive dative of ea then why is it introduced to us in this module on accusative pronouns? And what is ii (with a hat on the first i) which isn't in the table of accusative pronouns at all? I've just re-read the possessive pronouns section and now understand that ei is one of the female 3rd person singular possesive pronouns - that is its place here and why it indicates that it is her parents not his - is that the same as saying it is genitive-dative (we don't have the 5 cases in English as such hence je ne comprend pas!)...
Why do i feel like ii with a hat on the first i didn't appear in the tips table?