I kinda grew up conditioned to the "twinship" idea, that while it is not trivial to find highly similar others, it is possible and is one of the most rewarding social experiences. A key person in this context for me was my father, but also a few good friends in childhood and adolescence.

But the OP very much reminds me of how and why I got interested in existential philosophy in my teens / 20's, when I started to realize more and more how we all are unique and individuals and, ultimately, mostly alone in our deepest endeavors. I felt very strongly drawn to that realization and explored those philosophical ideas in my youth in depth; it also colored my value system and spiritual endeavors.

Gradually I lost the connection with those darker existential thoughts and feelings starting in my late 30's, when I had lots of opportunities to experience team work, community, steady close relationships, reconnected with my elderly father, and meaningful friendships with several people who liked to ponder similar existential questions and were prone to similar existential angst to mine (easy to find some now even here on PC). Those earlier life feelings have not returned to me since (I am 44 now and feel well-integrated into society, with a strong grip on my niche and social roles). Those earlier feelings of alienation, occasional void, the compulsions to try and compensate for feeling different inside and getting external "validation" how others indeed saw me very different... it's mostly dissipated from my thoughts and vanished from my emotions. I's a bit like a loop back to my very early life origins, when I felt so close and comfortable in my immediate family of origin, just a much broader and higher level of connectedness. It's a wonderful and steady feeling for me now but it's come at a cost during my 30's (not getting into the details of it now) that I am not sure I would choose to pay again had I had the chance to redo it. All of it is intimately hardwired into me now but I am not sure the alienation will never come back. My father suffered the worst of it during the last ~2 years of his life, so... I am trying to enjoy the connectedness feeling as long as it lasts.