It's a hard one to work through. My brother's ex, was very hostile to the new partner, and effectively poisoned his DS and DD against his new partner, so they felt to please their mum, they pretended they didn't want to visit on the week-ends, as it "would make Mummy cry", there is an awful lot of bitter, selfish, use of kids as weapons to get back at the ex, even though she was the one who ended the relationship! We made sure that the kids always knew that we all loved them, and the door was open for them any time. Use of technology like Skype and Whatsapp was invaluable to us, and when the kids got older, they realised that we were not the ones at fault!