Possessive Adjectives accompany a noun.

tu perro
      your dog
su pelota
      his/her ball

They must agree in number with the noun.

tus gatos
      your cats
sus libros
      their books

The vosotros form (used in Spain) agrees in gender as well.

     vuestro carro
      your all's car
     vuestras familias
      your all's families

Stressed possessive adjectives go after the noun.

los boletos tuyos
      your tickets
las cobijas suyas
      their blankets
las almohadas tuyas
      your pillows