"Our cup is between the plates."
Translation:Nuestra taza está entre los platos.
c3sound- the article has nothing to do with the persons, only with the object possessed. nuestro goes with masculine noun, nuestros perros, nuestros libros. For a feminine noun, no matter if it's a bunch of boys who possess the thing. Nuestra silla es roja, even if the silla belongs to a boy. Our chair is red.
estar is a temporary use of the verb "to be" for example "I am sick" is a temporary state to be in because soon you will get well. If you have a happy disposition in general, however, that is permanent. You would then use the verb ser to say for example, "ella es contenta"