My DD father is also one of my best friends. We didn't work as a couple but he is an amazing person. He attended my wedding 2 years ago even driving me to the venue.
Last week he got engaged to his GF and they are expecting a baby soon. I am so happy for him on both fronts.
My soon to be ExDH says it's wrong to be so happy and excited for them. He says it's confusing the children. I don't see how being happy for a good friend is bad. AIBU or is ex just messing with my head again.