In David Cronenberg's 1986 adaptation of The Fly, Jeff Goldblum's half-man, half-insect hybrid goes insane and tries to merge his body with a pregnant Geena Davis to create "the ultimate family."
A less gruesome instinct informs the work of photographer Ulric Collette, who fuses family members together, bilateral symmetry be darned. In his "Genetic Portraits" series, Collette combines parents, children, cousins, and siblings Harvey-Dent-style to highlight the subtle genetic differences between relatives. Here's a sampling of his portraiture, which you can find more of on his website.
Daughter and father: Ariane, 13 and André, 55
Son and father: Nathan, 9 and Ulric, 32
Daughter and father: Amélie, 33 and Daniel, 60
Twin brother and sister: Alex & Sandrine, 20
Father and son: Laval, 56 and Vincent, 29
And for more heartwarming snapshots in the vein of 1980s horror flicks, check out Collette's Facade series. This group of photos is currently on display in Montreal and blends individuals' faces on the same heads, resulting in portraits of Thing-like proportions. [Via MeFi]