Legal Question in Credit and Debt Law in California

You have no right or way to place a lien on the house. You have to sue your brother and sister and then maybe file a notice called a lis pendens that says that you are claiming an interest in the house so that everyone knows that you are making a demand for payment of money owed. You need to see a lawyer about the type of lawsuit you can file and what you can claim that would give you the right to file that lis pendens (which means "lawsuit pending affecting the title to the house"). Most likely all you can do is just sue your brother and sister in law for the money since it was just a loan and can't stop the sale of the house (unless you were promised that the house was going to secure your loan) .... but you need to consult with a real estate lawyer immediately. Not sure if anything can be done in the divorce to claim the loan but for that you might have to consult with a lawyer that handles divorces.