Might be time to consider suggesting that your cousin hire an estate attorney paid for by the estate, to help navigate all these issues in a unbias and informed manner. Make sure things are done correctly and fairly, with as little stress as possible.

Was the property split evenly between all parties? If so I'm not sure I understand the issue of potentially owing others. Also keep in mind for the future that someone will need to pay property taxes (assuming your state has them) on the property and deal with any income it generates. Some a trust or something might not be a bad idea to deal with this. That's where a professional could give good advice as it sounds like it's more complex than anyone's experience level.