Legal Question in Real Estate Law in California

Well, technically, "forgery" is a crime, and only "the People" can file a complaint for a crime (at least usually), and this is done by a district attorney.

However, an ordinary citizen can file a civil complaint for something closely akin to forgery, in this case probably "fraud", and have the case heard by a judge in a civil trial.

In addition, it is not uncommon for civil plaintiffs to file lawsuits making somewhat conflicting claims in two or more separate "causes of action" in the same complaint. The principal thing to avoid in putting together a multiple cause of action complaint is to avoid alleging facts that are necessarily contradictory; i.e., one would not allege that plaintiff was a resident of California on 1/1/2014 in one place and then allege that he was a resident of Ecuador at the same time in another paragraph of the complaint.

Also, a fraud resulting from falsification of a signature could also be a form of breach of the same agreement.

A note of caution: Not every instance of someone else writing your name in a blank in a contract is necessarily improper. A person could be acting as your agent in signing your name, for example. There is an extensive body of law dealing with when someone has become an agent, and for what purposes, and when and how the agent may sign for the principal, and so on.

I'd recommend asking a local attorney for a free consultation to discuss whether the wrongdoing can probably be proven based on your evidence, and what causes of action should be pleaded in your proposed suit.