How can narc ex totally cut our daughters out of his life?

I split with my narc ex 3 yrs ago. Although I left him I struggled to come to terms with my grief. The man I lost did not exist, my pain was all in vain. After being told about narcisstic abuse my healing process started. The part I still struggle with is how he refuses to have any contact with the girls, never acknowledges their birthdays or even stops his car to speak to them. It is beyond my understanding how he can live with himself. To top it all he has a girlfriend with 2 children of her own and they now have a baby together. How can he not love our girls. Does he lovd her children and the new baby? It hurts so much as my girls mean the world to me.