This problem of fever
which is ongoing in a cyclic manner and history od autoimmune disorder in the family. This all suggest towards an autoimmune etiology or cause and this can only be diagnosed by doing the proper investigation to make sure the immune system is the main reason for the condition.
If the treament history include steroids
for these types of episodes and there is improvement in the condition with the steriods, than it makes the autoimmune theory more stronge.
I would suggest you to consult some immunologist, who is specilist on immunological condittion regarding this problem to rule out or confirm the cause for this condition.
Thanks and take care.