What are the duties incumbent upon a stepfather towards his wife's children from her first marriage? Does he have the right to command them to pray or compel them to do so? Is it permissible for the son to address his mother's husband as "father"?

The guardian of a child must command him to pray when he reaches seven years of age, and discipline him for it with striking and admonishment when he reaches ten years, based on the saying of the Prophet, peace and blessings be upon him: "Command the child to pray when he reaches seven years," and "Strike him for it at ten." This discipline is to accustom him to prayer, and it includes both male and female. It is permissible for the guardian of an orphan to discipline him with what benefits him.