Legal Question in Real Estate Law in California

Yes, you probably have some legal rights, at least to a minority interest in the house, based on having paid for part of the equity through making payments on it. In addition, if you can establish that the rest of the equity was a gift (through adequate proof such as testimony of the people he told it was a gift, for example), you may be able to convince a court to give you full ownership. Keep in mind that bringing any kind of legal action against his father/your after in law will be long-term damaging to family ties (if any now exist), so sometimes in-family negotiation is better than jumping into a lawsuit. Confer with a local real-estate attorney, and mention "pro-tanto interests" (relative to your making payments) and gifts (relative to his expressed intent at the time you moved in. There are some other legal theories that might also strengthen your case.