Using the correct pronoun is:
Nosotros estamos hechos de estrellas
Nosotros hemos sido hechos de estrellas
If I say "hemos hecho de estrellas" it sounds incomplete, like to say "I made this... of plasticine", but what did I do? The complete sentence would be: "hemos hecho UN HOMBRE de estrellas" Maybe the Goods would say that.
-Hemos- need to be plural because the corresponding pronoun (nosotros:we) is plural. In english we must say: You are, and not say: You is.