Prompting fascination and fear since mythological times, twins continue to haunt our imagination. Identical, non-identical, conjoined, mutant, telepathic, homicidal, buddies, soul-mates or jealous rivals, twins feature in scores of films across a range of genres; comedy, drama, thriller, horror, sci-fi, action and auteur cinema. Amidst this apparently infinite variety, however, insistent patterns occur (De Nooy and Statham, 1998). In this paper we focus on a particular sub-set of twin films -- recent horror films featuring male conjoined twins -- to show some surprising regularities of representation. Specifically, these narratives of fraternal attachment and separation represent the twin relation as maternal. Our aim is twofold, to demonstrate this striking pattern (in our analysis of Dead Ringers, Basket Case I and II, an episode of The X-Files, and The Dark Half) and to account for it. We argue that existing work on the representation of the body in contemporary horror only partially explains the emergence of this phenomenon, and that the pattern needs to be understood as a highly specific configuration of genre (horror), gender (male) and topos (conjoined twins) that lends itself to the rehearsal of a cultural anxiety regarding gender (male maternity). The discursive power of this configuration is demonstrated in our reading of Twin Falls Idaho. This film is not in the horror genre, and it repeatedly uses the metaphor of marriage, rather than motherhood, to describe conjoined twins Francis and Blake’s relationship. And yet this text too must negotiate the pattern we have identified, making numerous gestures to displace and deflect maternal references. These remain, nonetheless, an undercurrent in the film, an indication of the force of this discursive phenomenon.