I am so sorry to hear about your dilemma, and I absolutely share your pain. At my wedding, we had two sets of divorced and remarried parents to deal with, and neither of the mothers had ever got over their ancient divorces despite being remarried for years. They all said they would come, but only if they didn’t have to be near their exes. We made an effort to give each of them some special role (helping choose the menu, readings, music, wine) so they all felt included and invested, and TBH so they were reminded that it was about us, not them. The top table plan needed the diplomatic skills of Henry Kissinger! But it was worth it and they didn’t make a drama on the day.
As this is the bride’s grandmother, you could try making a real fuss of her, involving her in choices, allocating her favourite grandson to sit with her, have a group of trusted relatives/friends to take it in turns to chat to her, etc. Or invite her best friend(s) (I did that too). It may partly be fear of being on her own when your father is happily with someone else. In a worst case scenario, invite her to the wedding and your father and his wife to the evening do. But it would be very special for your niece to have everyone there at the same time and not making a drama. Good luck x

We had this situation at our wedding, and my sister in law before us. In our case it was the mother who left for and has a “new” partner (30 years) and the father who remained single / not over it.

My sister in law chose not to invite the partner, which led to her mother refusing to attend. The father attended.

In our case we tried to resolve it - suggested that they all come but only the parents sit at the top table (the “new” partner at a guest table). This wasn’t acceptable though, and in our case the father refused to come.

So for the siblings, they each just had one parent at their wedding.

Very sad, and I was shocked that they couldn’t all put it past them for one day. But you must do what you feel most comfortable with, let them make their choices, have difficult conversations and then just try to not let any upset or anger seep into life afterwards.

A horribly difficult situation, you have my sympathy.

You had me at “my mother brought us up on her own”.

If she feels that strongly that she won’t come to the wedding if your father’s partner is there, then ask him to come by himself.

If he refuses to come without his partner, then that’s his decision, but your mother brought you up so she simply has to be there, and to me this seems like the solution that she wants, and that will not upset her.

I hope this helps, what a terribly tricky situation to be in.

I am hoping that someone here can help with a situation my sister is facing as it is coming down the track for me as well. 

Our parents divorced well over 20 years ago. 

My father left her for another woman who is still with today. I guess she was the right woman for him. 

The split was very very acrimonious then and my mother has never got over it. 

My father was present in our lives but it is fair to say that my mother brought us up on her own. 

My niece is getting married and my father, my nieces grandfather, want to bring his now wife. My mother, my nieces grandmother, is adamant that if his wife comes, she wont attend the wedding. 

This is all proving very stressful for my sister and neice. Not sure what the best way forward is without upsetting my mother dreadfully. I’d like to add that I honeslty feel my mothers behaviour is coming from a place of fear, she really has never got over the divorce, so I’m not sure if she could even be in the same room as him.