Does "5 Year Look Back" apply?

[cousins]

My father, his sister and her husband owned a very small piece of property in Kentucky (1/8 acre) and the mobile home on it. Only my father resided there before his death in 2000 and all owners are deceased. As the property taxes have not been paid for 5-6 years, the county has contacted the heirs of the owners requesting payment, the heirs being me, my siblings and my cousin, the only child of the husband/wife owners. We would like to find a buyer once we take care of the back taxes but the troubling situation is the ownership of this property was inadvertently not claimed when my aunt entered a nursing home in Indiana and received Medicaid. Since all original owners no longer are living - deaths occurred in 1999 and 2000 - is my cousin liable for the non-reporting of the property to Indiana or can he, together with us, try to sell the property and be done with it?