How can someone put a lean against a home when they don't own or even have lease agreement

If your grandfather's estate is still open and the house has not yet been transferred from the estate to your parents, then the Executor needs to have your sister and her husband evicted, and then consult a real estate attorney for help getting the lien cleared off of the property title. If the lien is the result of a personal liability that either your sister or her husband had, it should not have been placed against a property that did not belong to them. However, they may have forged paperwork showing that they did own the property, or otherwise lied to the lienholder, and that means that the title to the property will need to be cleared. If the property had already been transferred to your parents from your grandfather's estate, then your parents will be the ones who need to take the next steps. But start by getting the sister and her husband evicted as soon as possible. Either way, consult a real estate attorney for help.