I agree with the advice above, although I do think you should keep the words you write as simple as possible because you have never spoken to her. Unless you know his marriage was a happy one, it's best not to say something about his second marriage. Presumably you met his sister, so if you write to her you will have memories you can share. radicalnan is right that reaching out is a good idea. Everyone's loss will be different and don't be surprised if you find memories popping in to your mind for a while. His death is a loss for you too, especially when you have children in common.
Good Morning Tuesday 30th April 2024