Normal feelings?

Please don't attack me. First time being a step parent. All I want is to hear other's experience and wisdom.

My partner has a beautiful 7yp daughter and the other day they had a cute moment and he basically listed his "favorite girls" in the order 1. His daughter 2. Myself

Bottom of the list he said her mom (BM) He never has anything good to say about their Mom. She's not too high conflict from what I have experienced - she's just not too mature and has made some wrong choices in her life.

Anyways, this for some reason rubbed me the wrong way and it's shifted my thoughts about things... And I'm also ruminating about how with a blended family can you truly put your relationship above the kids? In my previous marriage with my BD we had the understanding our marriage and relationship came before our children in the usual sense that our relationship needed to be strong and prioritized to set an example for our children. How is that possible in a blended family? Obviously I will never know the dynamics of a father-daghter relationship but is this normal and it's just something I'm newly experiencing and learning about? Please be kind. Reminder, You can simply say it's normal and not attack me lol