Is my Step Father's wife mahram for me

My mother married 2nd time when I was 2 or 3 years old, and my step Father already married and have 2 children with her 1st wife, recently my step father passed away, Is 1st wife of my step father stil mahram to me and what about my step siblings. What are the ruling related to marriage step mother (wife of step dad) as my step Father is not my blood related so what about his wife (his 1st wife), and does she has to do parda in front of me.