This is the 14427th most frequent Spanish word.
vuestro
"Vuestro" means "your" (plural, belonging to all of you, informal in Spain).
The word 'vuestro' is used as a possessive pronoun referring to 'your' in plural, addressing a group informally in this context.
¿Habéis terminado vuestro proyecto escolar?
Have you finished your school project?
Here, 'vuestro' acts as a possessive pronoun indicating ownership by a group addressed informally, describing the dog belonging to that group.
Vuestro perro es muy tranquilo.
Your dog is very calm.
In this sentence, 'vuestra' modifies 'familia', showing possession by the group referred to informally.