I think that some people are born to orbit the axis of another with the perfect valance...
In other words, atoms all have a certain number of electrons in their orbit and they seek to balance the charges of their outer electron's rings. This is called the valance charge.
Human beings are similar. We have others which provide our inner shells instead of our outer ones. Those others can be said to be twin flames only when their union produces not just a harmony of souls, but a transformation of both. Not even what is necessarily a union, as that implies they must meld and forsake something of themselves.
What we see with atom in valance is different. It's a balance which destroys components of neither individually, but creates a compound with new properties. Both, at the fundemental and individual level, are preserved and intact.
How many people can find their twin flames isn't a physical distance issue. It's an alchemical issue, because the individual who transforms themselves bends time and space around them and those with the correct charges are drawn into that field. It's a bioelectric field. Someone "shut down" (as I have recently been) either will not find this other or if the other is present, will not hold charge with them.
Since space is not an issue, it's enough simply for both to exist. Even when the other dies, they are preserved in the moments in which they were held by one another's spiritual presence. While it is preferable for both to acknowledge the existence of the other, even merely existing, even across aeons, will add something to the consciousness of a connected twin flame. If they were to combine...physically and aetherically and mutually conscious of each other, something beyond magical would occur to all humans. This is the ideal. But it is such a paradise of ideals that humanity, collectively, doesn't allow it to manifest very often.
More often, we are not allowed to permanently coexist with a twin flame. Perhaps if humanity were to be more facilitating of its own happiness, it would be a different story. Yet...it is not.
