I mean, who the hell were these "friends" and why haven't they ever popped up?

It's a good question. It's possible Lupin, say, might be one of them, but with him one wonders even more why there's never been any contact between them before. Did Harry just disappear from their point of view on the night of October 31, 1981?

it seems James was making all the choices in the Potter household and I suspect he was just going to wait for Sirius to marry.

Hm, a plausible idea.