Certainly, people can get along without siblings. Single children do, and there are people who have irreparably estranged relationships with their siblings who live full and satisfying lives, but to have siblings and not make the most of that resource is squandering one of the greatest interpersonal resources you'll ever have.
I've come to recognize what I call my 'inside interests.' Telling stories. And helping people tell their stories is a sort of interpersonal gardening. My work at NBC News was to report the news, but in hindsight, I often tried to look for some insight to share that might spark a moment of recognition in a viewer.