I cosigned a car loan about 12 years ago for my sister inlaw and now about 2 times a year I receive letters from the collections

Probably not. The statute of limitations (the time they have to sue you) is 4 years. The time runs from the day on which the last payment was made. So if neither you nor your sister in law have been paying on it, and they never filed suit, it is too late for them.

You should contact the collection people and notify them that the debt is disputed, and also pull your credit report, and make sure that it isn't on there. www.annualcreditreport.com gives you a free copy, once a year, from each credit agency.

Probably not. The statute of limitations is 4 years, which begins on the day that you or your sister in law last made a payment. If no one has been paying, and they never filed a lawsuit, then it is too late for them now.

You should notify them that the debt is disputed, and also check your credit report. www.annualcreditreport.com will give you a free copy.