I think my dad has other kids other than My Sister and I?

When I was around 5 my parents were still in a relationship. I remember going to this lady house I didn’t know and she two daughters around my age I don’t remember who was oldest or youngest between us. They were calling my father dad. I never really put much thought into but I never forgot about it. The lady seemed to be older than my parents. I’ve never asked my dad about I’m not sure if I asked my mom. I doubt she wouldn’t have told me. My dad wasn’t the best father all the time and I know it’s some women who would decide to take care of their children without the help of the father. How should I go about asking him? They might have called him dad because he was around so much. If it’s true I really wish I had a relationship with them

I think my dad has other kids other than My Sister and I?
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