Who really are heirs of the property?

my father has deceased in 2003 - leaving 3 kids behind. my father has 6 brothers and 1 sister. My father's father whom is my grandpa has also deceased in 2009. my grandpa owns a home but didnt leave a will or anything and my uncle who is residing there now says we are heirs of the property since my dad is deceased. what does this really mean? or how does this work? are all granpas kids heirs too or just my dad that has already ped?