This is the 2347th most frequent Spanish word.
suyos
"Yours" or "theirs," indicating possession.
In this sentence, 'suyos' is used as a possessive pronoun referring to something belonging to 'ellos' (them). It agrees in number and gender with 'los límites'.
Es importante respetar los límites suyos.
It is important to respect their boundaries.
Here, 'suyos' is once again a possessive pronoun, agreeing in number and gender (plural and masculine) with 'los perros'.
En este vecindario, los perros suyos siempre están bien cuidados.
In this neighborhood, their dogs are always well cared for.
In this example, 'suyos' refers to the ownership of the books by 'ellos/ellas', and it's singular masculine to match 'los libros'.