A pleading must be in writing and must be signed by all persons joining in it.
All pleadings filed in proceedings under the Probate Code must be verified. If two or more persons join in a pleading, it may be verified by any of them.
If a person is absent from the county where his or her attorney's office is located, or for some other cause is unable to sign or verify a pleading, the attorney may sign or verify it, unless the person is, or is seeking to become, a fiduciary appointed in the proceeding.
Cal. R. Ct. 7.103