Is it obligatory to wake up family members who perform night prayers (Qiyam al-Layl) upon waking up for night prayers, and is there any sin if they are not awakened?

You are not required to wake your family for the night vigil (Qiyam al-Layl). It is preferable to wake them to help them do good. However, what you are required to wake them for is the obligatory prayer if its time is running out.