I dunno, Demonic Underwear, sir.
I came from a large family, at the tail-end of it, with only one younger than myself.
It was a pretty contentious, harshly competitive, family, although whatever the problems were, existed long before I was born, and I could never make sense of the issues.
Over time, beginning when I was in college, they all started dying off; prematurely, and from diseases that afflict the affluent, those leading easy and comfortable and secure lives.
I'm the only one left.
I took them one at a time; there was never this urge, this yearning, for "one big family reunion," especially after the parents were dead. I got along with them all, although as individuals, not as all together, as one big family.
I think one's relationships with one's parents and one's children are the truly important ones; as for brothers and sisters, if one gets along really good, fine--but if one doesn't get along really good, well that's life.