It sounds to me that you placed your purchase offer with the listing agent for that property. While it is legal in California for one agent to represent both buyer and seller, there is some conflict of interest involved. You should have signed an Agency Disclosure with your agent, either before or at the time you made the offer. Please read it. The distinction in the agent's duties to buyer buyer and seller in such cases may seem small, but they are significant.
A real Estate contract is binding. Your offer becomes a contract once it has been signed by all parties and contigencies have been removed.
It is not clear where you are in your transaction. If it is your purchase offer that isn't being signed by all parties, there is nothing you can do but ask that your deposit be returned. If your offer was accepted by all the sellers, and you are in escrow, your agent needs to send the sellers a Notice to Perform. Your agent should be advising you in this matter, that's his job.
