Speaking as a step dad…. Although to be honest, one of my girls calls me dad, the other step dad, after 12 years of being there for them.
The biological dad floats in and out of their life, as it suits him. he is more concerned about ‘how it looks’ in his dealings than the impact on his children. He gets a new partner, he gets involved with his first kids for 2 months, when he has big family things, like a wedding (including his own) he makes an effort to woo his girls back and then pay for dresses and transport to the event - then they don’t hear from him for 6 months, in one case he went 6 years without contact.
I met mum about 3 months after their separation, treaded very carefully, allowed the kids to determine their terminology for me, chose not to be hurt when in the early stages strangers would mention “you’re dad” in relation to me, and they would shout “he’s not my dad”. (Decided to own that, and get in earlier and say, I’m not their dad or I’m mums boyfriend).
12 years on, dad, step/dad whatever, I think it meant something once, but I think of them as my daughters, I will likely pay for their house deposits, weddings, I have two grandchildren from them and I’m referred to as grandad by the one who still uses step. I think the only bit that might hurt is the walking down the aisle bit, because I expect one of them to ask sperm doner as they refer to him.
Labels. We can choose to be upset, but actions always speak louder for me.
Love my daughters, even if I’m not their biological father.