My parents divorced 20 years ago,although it was a mutual parting of ways it was very messy and they don't like each other/speak (there were no 'other parties' involved btw.)
They have both been married divorced since. DM is now single and has been for 3 years. Since 2nd divorce my Dad was with a woman for a yr who DM didn't like (she was very nice) and made a (private) fuss whenever said woman came to a family get together.
Dad now has a girlfriend he's been with for about a year, she's also nice, DM has met her and they seemed to get on. DD really likes the new GF's granddaughters and has invited them to her bday party. DM is very upset and doesn't want them or new GF to come and told me so yesterday... She is also upset I invited them and hadn't yet invited her, something which I planned to do but have been run off my feet with DC.
Soooo, I think DM is BU, I am fucking sick of being stuck in the middle of my parents childish animosity, it's DD's party FGS!