The problem with many men now is that they resemble mice and behave like bears. A Muslim is responsible for his family. Allah has ordered us to save ourselves and our families from the fire whose fuel is people and stones. As such, fathers, or other adult household members, with the mother, have the responsibility of raising children who truly believe and understand their religion. This is something that requires much attention, and is a great responsibility, particularly in the West. Children have to be raised loving Allah and His Messenger (Allah bless him and give him peace), and the way of the Muslims. Such children would not normally question applying the rulings of Islam.
Now, when none of this has been done, the ruling of course remains: it is obligatory for the wife/sister/mother to cover. Her not doing so is an evil (munkar). The other household members are obliged to try to get her to cover, while this is most incumbent on her husband or father...Not surprisingly, husbands or fathers are also the ones who may take it upon themselves to restore a family's "honour" should the wife/sister/mother refuse to cover up.