Bonjour Nan !
"Vous êtes des parents." means "You are parents." in a general way, i.e. you have children.
Here "des" is the indefinite article, see the related lesson: https://progress.lawlessfrench.com/revision/grammar/plural-of-the-and-a-les-and-des-articles
You could also say "Vous êtes les parents." which would be specific to a given situation ("You are the parents (of that child)").
I hope that's helpful!
À bientôt !
