Questions & Answers about Я знаю этих актёров и люблю их фильмы.
Why is it этих актёров and not эти актёры?
In this sentence, the actors are the direct object of the verb "to know," so they need the Accusative case. Because "actors" are living beings (animate) and plural, their Accusative plural form looks exactly like their Genitive plural form. That's why we use этих актёров.
In the second half of the sentence, "films" is also a direct object. Why doesn't фильмы take a Genitive ending like the actors did?
This is the big difference between living and non-living things in the plural! Since films are not alive (inanimate), their Accusative plural form is exactly the same as their basic dictionary plural (Nominative). So фильмы stays фильмы, while the animate actors had to change to актёров.
Why doesn't the word for "their" (их) change its ending to match фильмы?
Unlike words for "my" (мой) or "your" (твой), the Russian words for "his," "hers," and "their" (его, её, их) are "frozen" and never change. They stay exactly the same no matter what case the noun is in.
Where does the "л" in люблю come from if the dictionary form is любить?