The Supers were sick of running/fighting the Community, so they banded together and waged war on The Community. In the end no side won, but one-fourth of the supers disbanded into Australia, as it was a somewhat of a safe-haven at the time.
The Community dates back to Middle Ages(5th-15th) century. One man created The Community, an underground organisation that hunted down the Supers. The man and his followers believed them to be witches. Maybe they were.
The power gene skips every second generation eg. Tom has it, his son Tim doesn't, but Tim's son Billy does.
It is rare for supers to have siblings, the rarity goes; Bro/Sis, Bro/Bro or Sis/Sis, Twins, Triplets, anything higher than triplets is unheard of. Having three or more children with the gene is very, very rare.
Most super have two powers; one to do with their body and the other to do with their hands. Some supers only have one power. Supers can have other ways of getting extra powers.