If they heard about islam and refused to accept it, they are kafir and died as kafir.

I am a revert of 10 years Hamdullilah. My parents were good living roman catholic and are dead many years. I assumed they were destined for Hell because they believed in the trinity. – major shirk. I have read my Quran many times and for me it is clear that Allah will not forgive this sin. However a muslim wife of my husbands cousin said not to say this and only Allah can judge. Please clarify.