This is the 12992nd most frequent Spanish word.
pertenecían
"They belonged."
In this sentence, 'pertenecían' is used to indicate ownership or association, showing that the books are owned by or associated with the library.
Los libros pertenecían a la biblioteca.
The books belonged to the library.
Here, 'pertenecían' describes a previous state of ownership or association, emphasizing the temporal aspect with 'antes' (before).
Antes, estas tierras pertenecían a la familia de mi abuelo.
In the past, these lands belonged to my grandfather's family.
'Pertenecían' in this context denotes affiliation, suggesting that the customs were characteristic of or originated from an ancient culture.