Some of the most virulent public trans-exclusionary radical feminist (TERF) discourse in the UK follows the grammatical form of the third conditional: if I had grown up now, I would have been persuaded to transition. This articulation of the hypothetical threat of a transition that did not happen but is imagined, in retrospect, to be not just possible but forcibly enacted plays an important role, both politically and psychically, in a contemporary political landscape that is threatening the livelihoods of trans children. Interrogating this discourse via an analysis of an open letter by J.K. Rowling, and a documentary by Stella O’Malley, this article asks: what might we learn about contemporary transphobia in the UK if we took seriously the grammar of TERF discourse animated by trans childhood? It argues that while the third conditional grammar of TERF discourse could articulate a politics of solidarity between cis and trans positionalities and politics, its potential for a shared political standpoint is routinely interrupted by the defence mechanisms that are oriented by the psychic life of the child. Interrogating these defence mechanisms at the level of the cultural, the article traces out paranoia (as reading practice and psychic state) as well as projection, as two main modes of TERF engagement with trans childhood. The article thus engages with the range of real and fantasmatic impossibilities that haunt the trans child both in the present and the past, and it contributes to the growing body of scholarship on trans childhoods. In doing so, it makes the case that public discourse on trans children should desist from hypothetical third conditional claims, and instead find ways of embracing trans childhoods unconditionally.