We took it out of a credit card account, originally one of mine but later rolled over to a couple of hers. We had a promissory note that provided they would pay whatever interest was charged by the credit card. That became problematical because I had to pay off the card faster than they were paying us. Thus we eventually assigned the debt to some cards she was paying on, because otherwise we would still be paying interest and they would not.
When they got divorced, the ex-SIL agreed in the papers to be responsible for the $5700. That was 2 years ago so when we filed, we added another $1000 in interest (7.9%).
Since we had both the promissory note and a copy of the signed marital dissolution agreement, along with the corresponding credit card statements where we borrowed the money for them and what my wife is paying in interest now, we had a well documented case. However, there were some vulnerabilites that Judge Judy might have jumped on. Like, why did we take so long, did we contact him before suing, why are we not suing the daughter (because the legal experts among us would gladly remind me that we were not to a party to the divorce, so we could still go after her), did we really expect to get repaid, and would we be in court if they were still married. We had answers ready: he sold his house and disappeared after the divorce, and we finally located him at his job through a mutual friend; much of the money went into his house; and since they were paying in dribs and drabs, we indeed might not be in court if they were still married. We might also have argued, though our daughter was not a witness, that she must have given up something in order for him to agree to pay us.
So we appeared in our local courthouse last Friday, and the outcome was ...
Spoiler
He didn't show up, so we got a default judgment for $6,700. Wish us luck collecting it, however.