Bonjour Cheryl, I am quite uncertain of the meaning of your question. C'est and ce sont are both demonstrative pronouns. Would you be so kind as to clarify the meaning of «before a pronoun»? Merci,

It's ok I've worked it out myself - I think!. It's only C'est when it's a adjective or adverb. Pronouns like miennes would still be Ce sont???

It would, e.g., be "Les valises, ce sont les miennes." I hope that was your question.

-- Chris. (not a native speaker)