OK I need to know for sure if my siblings were legally adopted by their step father. They all have his last name, but their mother could have just changed their name. I'm wondering because well honestly my dad has dementia. And is going crazy. Slowly losing his mind. Well for legal reasons and just because I'd like to know if my brothers and sisters are really my siblings. And if so. We need a probate lawyer and will made and all that. If not, then, legally its just me. And also, I don't think so, but would my half sister from my mom have any rights here? Since he did raise her.