Legal Question in Real Estate Law in California

You are going to have to speak to an attorney. My first question would be: "Was any of this in writing?"

This could either be a huge fraud on you, or perfectly proper. Or, it could be a fraud on you that you can't do anything about any more, due to the passage of time. I'd have to know quite a bit more, including when the first sale occurred, how title was held prior to the first sale, whether you have spoken to your mother and/or sister about the transactions, and so on. Please feel free to contact me, if you'd like, for a no-cost analysis of your situation.

The obvious answer is that you either informally resolve your claims, or you file suit if there is a legal basis to do so. You may have HAD rights as an 'heir' to file a probate claim after the death of the parents, but it sounds like that was a long time ago. If so, you are too late. Contact a 'estate and probate' attorney in your area with the dates info.