Should my mom tell her grand daughters why their mom left?

My brother and his ex wife divorced last year after 7 years of marriage. Both of my nieces were 6 and 4 years old when it happened. My brother's wife had cheated one on him three times during 2019-2022 and each time he took her back like nothing happened. It was only for the girls as he didn't want them living without a mother. Now the girls are 10/8 and can't visit since their mom gives my brother every Thursday and the weekend for 2 hours. I heard my mom saying that one of these days both our nieces will come looking for us when they are older. She wants to tell them the truth about why things happen. I just don't think both would understand cause they never wanted nothing to do with us when they were younger. They always preferred their other grandparents (ex wife) since they lived with them now. If the girls ever came to my parents house and wanted to see us, they would be welcome though I would probably be curious about what happened during those years we didn't see them.

Should my mom tell her grand daughters why their mom left?
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