Answer: after "Caleb"
In this case, a comma is needed after "Caleb" because the phrase "who are members of the drama club" is an appositive.
An appositive is a phrase which follows a noun or noun phrase and provides further information about it. This phrase is usually unnecessary to the rest of the sentence, and is only included in order to expand on the information of the noun. Appositives are always framed by commas.