The premise is we are stronger in groups.
Meh, **** groups. I've always preferred one on one. Because it's those situations in which you can be the most real, and not be judged for it. Sides, I think the desire to have another in your life is a purely selfish desire.
In a sense I thing Freud was onto something with the concept of us seeking partners that resemble our parents. But just not in the weird sexual way.. what we do seek is for someone to look upon us as our parents once did when we were babies or young children.
In growing up, we progressively lose that sense of being unconditionally loved by someone. And so we spend much of our adult lives trying to regain that feeling.
As a baby, anyone walking past may look upon you in a manner that makes you feel loved. But even in the latter stages of being a baby/toddler, you may notice fewer people looking upon you in that manner.
For me that was the first step (in clear memory) towards realizing that this world is flawed.
From there it's all about 'growing up', 'becoming an individual' and progressively losing anything that made me truly happy. Not that my childhood was all that happy to begin with, what with all the abuse, neglect, abandonment .etc.
I too used to be able to shrug off lonliness for even decades at a time, but now that I'm 40, on disability, and stuck in a tiny town during a pandemic; it's staring me right in the face on a daily basis.