His stepfather’s name was Lolo Soetoro. He died long ago.
One interesting factoid. When Bambi was in Indonesia, he went by the name Barry Soetoro. Now, normally a child does not take the name of his mother’s new husband when his father is still alive. Which suggests that his parents were never married, and that he was not known as Barack Obama during the first part of his life.
I suspect he was Barry Durham at birth, and later changed to Barack Obama