You would be well-advised to discuss this with a commercial litigation attorney in your state. A little guidance can go a long way in a situation like this, and if you are nearing trial, it is especially important to understand the procedures and possible outcomes you will be facing.
Based only on this limited information, a principal question will be about the nature of the "work" provided by your stepfather, and whether there was any agreement or expectation of payment for that "work". Unjust enrichment is an equitable principle that applies where there is value retained by someone (you) due to the efforts of another (stepfather), and where it would be unjust to allow that person (you) to retain the benefit without payment. The boundaries of this doctrine under FL law as it may apply to your case is something that you should discuss with a lawyer licensed in your jurisdiction.
Benjamin Nivison is an attorney licensed to practice law in Washington State. This communication does not create an attorney-client relationship between you and Mr. Nivison, nor does it constitute specific advice for your particular legal matter. The information provided in this communication is for general reference and informational purposes only, and therefore should not be relied on as legal advice. Legal issues are by their nature complex, and any person with a legal question should fully consult with a qualified attorney.
Unjust enrichment is a cause of action sounding in equity whereby the plaintiff alleges:
1. The Plaintiff conferred a benefit on the Defendant;
2. The Defendant knew and appreciated the benefit;
3. It would be inequitable to allow the Defendant to retain the benefit without paying its value.
It sounds like you have a very serious dispute of facts. Such dispute will require rigorous factual and legal investigation, concomitant with discovery. You should engage an attorney immediately to assist in your defense.