This is the 369th most frequent Greek word.
αυτών
"Their" (possessive pronoun).
In this sentence, 'αυτών' is used as a possessive pronoun indicating 'of these'. It refers to 'των ανθρώπων', specifying ownership of the houses.
Τα σπίτια αυτών των ανθρώπων είναι όμορφα.
The houses of these people are beautiful.
In this case, 'αυτών' operates as a possessive linked to 'οι απόψεις', implying ownership or association between the opinions and an understood group of individuals.
Οι απόψεις αυτών παραμένουν άγνωστες.
The opinions of these people remain unknown.
Here, 'αυτών' again acts as a possessive pronoun, referring to an unspecified noun from the context, likely a group of people whose children excelled.