Narcissistic ex ignores our kids but plays daddy to others

My narcissistic ex, the father of my 2 kids lives as if his kids don’t exist. At the beginning of our breakup, he would pretend to care about them by texting non stop, the texts would start of about the kids and turn it all about me. In the last 6 months he has been with a single mum, got her pregnant and left, then moved onto another single mum, used her and left now is on his 3rd relationship to a young single mum. While he is with these women he does not even consider his own children and would rather be all about the latest women and her kids. This is the first relationship he isn’t silent about and/or trying to hide. How do I, as a single mum myself struggling with the fact he chooses to live without them and without supporting them deal with knowing and hearing about him playing daddy to everyone else’s kids. I’m in no way jealous of him or his girlfriends, I’m just beyond hurt, angry and disappointed he treats my kids the way he does, especially when they are 5 & 7 and totally understand they aren’t a priority to him. Most days I don’t even give it a thought, but the days I do, I feel so angry with him and with myself for even dealing with him all together, I feel sad for my children, I am full of regret and unfairness.. sorry just needed to vent