Escape Tax Assessment Mess

My father passed away this May and we just received a big surprise when the assessors office told us over the phone that a huge mistake had been made on their part. My uncle had passed away 20 years ago, and his portion of our family home was never assessed even though my dad did everything right on his part in filing the necessary papers. Even though my siblings and I have inherited the property, the assessor’s office told us that we still owe at least 4 years reassessed property backtaxes. I would also like to add that the escape tax was discovered by chance during a phone call to the assessor recorder because my sister had some questions about filling out the forms. This gave the assessor the chance to do the reassessment before we could make out a new deed to our names. Since my father had already passed away, are we still liable for paying the taxes?