Is congregational prayer obligatory or Sunnah, and is it permissible to avail oneself of the dispensation of considering it Sunnah if one's family prevents one from going to the mosque at night?

Congregational prayer is obligatory in our view, but most of those who deem it obligatory do not stipulate that it must be in the mosque; performing it at home is sufficient. Fear of harm permits abstaining from it. If you fear harm by going out to the mosque, then pray in congregation at your home with your family. If there is no real danger, then be diligent in attending it at the mosque. If your family prevents you, and you can pray in congregation at home, then there is no sin. Otherwise, do not obey them unless they compel you. Whoever emulates those who consider it supererogatory, then that is between him and them.