Mid 50s here with 2 DC late 20s. Neither one wants children. One said they may possibly want one maybe sometimes in the future - mid 30s - but the other one says 'no way, not ever.'
I feel weirdly about this and don't know how to articulate it. If they never have children, I will be fine with that, as it's their life, and I don't want them tying themselves down with children, because they think it's expected of them by family, and by society etc... But if they DO come to me and say they're expecting a baby, I will be over the moon. Basically, I will be happy with whatever they choose.
And I'm not just saying that, my life does not revolve around my (adult) children having children. I am not desperate for grandchildren, and to be honest, I find the constant Facebook posts from some friends/ acquaintances/ neighbours gushing over their grandchildren, every fucking day, (with 20 odd photos per week of them on there) bloody exhausting and annoying. It's like they have nothing in their life, but the grandchildren, and assume everyone else is interested in them, and those who don't have them are a bit jealous! 🙄 I have had to unfollow a number of women for this reason.
And as pps have said, I find small children exhausting, and some of them plain annoying. (I did not find my own like this though, they were impeccably behaved!
.... (Well, not bad kids/mostly quite easy.) 
I was late 20s/early 30s when I had them so had much more patience and energy. I think it's a myth that older mothers have more patience and tolerance than younger mothers. I had WAY more tolerance, and patience when I was late 20s/early 30s when mine were little. I would have had ZERO if I had had them at 40-43.
tl;dr @DGConcerns Your mum sounds exhausting, and like really hard work. Why is she so desperate for a grandchild? Is her life quite empty? Does she have no friends, or hobbies, or a job? Anything???