Is It A Mortal Sin Not To Forgive Others?

[Startoy]

I am very worried about my older brother who is 70 years old and in poor health and I am trying my best to help him get into Heaven. He is a Catholic and has not been catechized hardly at all and I am trying to teach him about forgiveness.

He said he has forgiven all his enemies but " I have some names in a file on a shelf and periodically ‘spank’ them from time to time";

I told him that I could write to y’all and see if it is a mortal sin to not forgive your enemies.
I believe it is but need your opinion; however, he did say he has forgiven his enemies but… if holding grudges like he is doing, is that true forgiveness?

Thank you and God bless all y’all!

.

 

[Augusta_Crowley]

The following links should help answer your question about forgiveness. If you have any further questions, please contact Catholic Answers directly.
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Recommended Reading:**

Scope of forgiveness
The Forgiveness of Sins
The Limits of Forgiveness