Hi there,
This sounds like a difficult situation. I think that it is unreasonable for your ex to dictate how / when you can see them when you have a new partner. I’m not sure the legal status of your separation – and how you’ve agreed to split time with the kids between you. Has your ex met your new partner – i understand they may want to meet them to understand who is seeing the kids. In order to be the best father to your kids you need to be happy – and if that means having a new partner – then it is the right thing to do and your ex needs to adapt