"Mea Tulpa, mea maxima Tulpa", as the young Dalai Lama would respond when his tutors asked him who ate the last Chocolate Hobnob

"Vanishing-twin syndrome," I announced, "is the new Birth Trauma."

"Have you been smoking the dried leeches again?" inquired tigris.

"They are for medicinal purposes only," I said. "I have just been appraised of the fact that embryonic, in-utero experiences are encoded in the epigenome and haunt our post-parturition lives as repressed memories. Specifically, the experience of sharing the womb with a fellow-blastocyte that did not survive the entire pregnancy, or even long enough to be detected. Anyway, vaping leech extract is different, all the cool kids are doing it."

"Fetus papyraceus does not appear to be in use as a band name," Another Kiwi helpfully vouchsafed.

If the Whackweedia is to be trusted (but it is a lying jade), then the Vanishing Twin phenomenon is already deeply entrenched within popular culture, as a plot device in House and Criminal Minds and such as... although the focus there has been on absorption of the weaker twin by the stronger, turning the survivor into a genetic chimæric mosaic.

More recent illustrations of graft
chimæræ in plants are available but
there is no point in owning an 80-year-
old familial copy of Science of Life if
one cannot pillage it for artwork

So it was inevitable that a psychologist [this being a term of art, here used to mean "shameless careerist bullshitter who informs Psychology Today-reading hipsters about the latest developments in self-obsessed neuroses"] would use the phenomenon to create a new psychological syndrome, and to stake out a new clientele for therapy, in which one's sense of dissatisfaction -- and the failure of consumer acquisitions to assuage one's sense of existential incompletion -- all arise from separation from a vanished womb-partner. I am not making this up:

Do you have a nagging intuition about someone in your life who feels vaguely missing? Odds are your intuition is correct. While there are many possible sources that your intuition is giving you fuzzy access to, one possibility is that you have a case of vanishing twin syndrome. As a therapist who specializes in couples therapy, I have found it very helpful for both partners when the reality of an intuition, including if its source is vanishing twin syndrome, is clarified.

The urge to create an immaterial psychic-emanation double of oneself, a Tulpa, stems from the same root. But it is not a proper syndrome until someone is promoting Re-Twinning Therapy. Alas, the Psych Today scamster has only progressed as far as Energy Therapy:

When I need to help my clients to uncover the very-early-in-life experiences that may have left residues of chronic intuitions that something was wrong, I find that energy therapy treatment methods are essential. For these, I ask one of the energy therapists in our office suite of multiple independent therapy professionals to join me for a session in which we work together, combining my conventional therapy techniques with their deeper-access energy methods.

(it is reassuring to know that Psych. Today is the voice of factual, empirical psychology, which has ousted the charlatans and magical thinkers who plagued the discipline in the past and gave it an undeserved reputation as a haunt of grifters).

Birth-trauma belief systems and the fad for parturition-dramaturgy were an entertaining feature of the 70s, apart from the occasional death when rebirthing therapists became over-enthusiastic with their reenactment of a difficult labour. My own invention of De-birthing therapy never caught on.

Re-Twinning Therapy is where you overcome the trauma of separation from the other self by re-enacting the whole inter-uterine experience more successfully, with nine months of close confinement on life-support followed by happy emergence into a wider universe. If nothing else, this will be a boon for recruiting people to migrate to Mars.

Alternative Beckett rebirthing-therapeutic title: 

Astride of a grave and a difficult birth. Down in the hole, lingeringly, the grave digger puts on the forceps.