“My mother passed away in February of this year. My father, of course, now has my younger siblings. He remarried about a year before my mother passed away. If something were to happen to him and he would pass away, who would get custody over my younger siblings? Neither I or my siblings care much for my step-mother whatsoever, she is trying to take over since my mom passed away. So if something would happen to my dad, and my step-mom never went and tried to get custody of them, where would they go? And would I be able to gain custody?”
If your step mother adopts, then she will be taking on rights and responsibilities vis a vis you and your siblings. In such a situation, she will have custodial rights should anything happen to your father. It would come down to the actual circumstances (loving environment, ability to provide, status quo, desire, ability, sibling ages and wishes, etc.) if there was a contest between you and step mother in the scenario where she has not already adopted and there is a struggle between you and her for adoption of your siblings. If she does not adopt, and does not want your siblings, and something happens to your father, then kinship adoption for you may be an option. Generally, the State would like to place children with family members. Assuming you are in a position to provide for them (over 18, employed, etc.), your ability to become involved with the care of your siblings would be superior to a stranger off the street.