Big Brother was the original, and in fact only founder of the party.

After seeing the corruption and evil of the old world, BB started the party to bring in a new golden age. Since BBs ideas were the greatest anyone has ever seen, everyone instantly agreed that only BB is fit to rule the world, and instantly surrendered (Except of course for our enemies, the Eurasians, however they can hardly be considered human).

As for when exactly, Big Brother has ascended beyond the concept of time, and has always existed throughout history. Perhaps one day we will be considered worthy enough to join him, but we should consider ourselves lucky we have a benevolent leader like Big Brother to help us see the light, and guide us in our eternal crusade against the Eastasians.

It sounds like your older friends are anti-revolutionary thought criminals, who seek to undermine the authority of the party, and I encourage you to report them at once.

Sources: Complete history of the party by Emmanuel Goldstien Big Brother