Is it permissible for the son of a wife to see the husband's mother and siblings without a hijab, and what are the rulings regarding stepdaughters in inheritance?

It is not permissible for an adolescent to look at non-mahram women if he comprehends matters concerning them, because he is like an adult and they are required to veil themselves from him. As for stepdaughters, they are mahram to their mother's husband if he has consummated the marriage with their mother. They do not inherit from him, nor does he inherit from them.