Legal Question in Family Law in California

You can. But as a practical matter such subpoena will almost guarantee to be quashed. The office staff is a third party witness who is not a party in the case. You must prove substantial hardship and necessity for the witness, which is a very high hurdle.

I diagree with Mr. Shen to some extent. You are going to get a motion to quash the subpoena, which will be based on attorney client privilege, attorney client confidentiality, and work product. Those privileges extend to the staff members of opposing counsel's office.