You can be sued if he defaults on a loan you co-signed. I don't understand the rest of your question because you are not giving enough facts. What property are they trying to lien and what is your involvement with that property. Is it your ex brother in law's property? Because they can pursue you both at the same time. Is this property in the state of Florida? Florida is not a community property state.
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I agree we need more facts to better answer your question. Based upon the limited information in your question, it would appear that youare liable for the debt, however, Florida does have laws that protect your homestead.
When you say "debtor", I believe you mean the lender. A lender is called the creditor. A creditor that sues you and gets a judgment against you, can place a lien on property that you own. If your name is not on the title to the property, no judgment against you will cause a lien to attach to that property.