Acclaimed BBC sci-fi series Orphan Black began with a woman encountering her doppelganger on a train platform, but by the end of the series it was revealed that there were actually hundreds of "Leda" clones in the world, as well as a set of male "Castor" clones. Tatiana Maslany played series protagonist Sarah Manning and the many other Leda clones, while the Castor clones were played by Ari Millen and first introduced in season 2.
Both the Leda and Castor clones were created by the Dyad Institute, but their upbringings were very different. The Leda clones were scattered across the world, birthed by surrogate mothers or by women seeking in-vitro fertility treatments. They were left unaware of their status as clones, and had monitors who insinuated themselves into their lives in order to keep an eye on them and create reports for Dyad. The Castor clones, however, were self-aware and were raised within the military.
The two sets of clones are named after figures in Greek mythology. Leda is a Spartan queen who, in her most famous myth, was raped by Zeus in the guise of a swan. Castor was one of her sons, whose father was the mortal king that Leda married, but who had a twin brother, Pollux, fathered by Zeus. When Castor was fatally wounded in a fight, Pollux chose to share his immortality with his twin brother so that they could stay together, and they were said to have formed the Gemini star constellation. In Orphan Black, both the Castor and the Leda clones actually come from the same source: a woman called Kendall Malone, who had a rare genetic make-up that allowed her to provide cell lines for both the male and female clones. But exactly how many of the Leda and Castor clones were made?
There Are 276 Leda Clones
The true number of Leda clones is revealed in Orphan Black's series finale, "To Right the Wrongs of Many," when Felix obtains a list of all the clones being watched by Dyad. The list has 274 names on it, but there were two clones who are not on the list: Sarah and Helena. Their birth mother, Amelia, grew wary of what the Dyad Institute had planned for her daughters and managed to hide them away, giving one to the church and one to the state. Sarah, an "orphan in the black," was put into the foster system and raised by Siobhan Sadler, while Helena unfortunately ended up in the hands of the Proletheans. Assuming that Sarah and Helena were the only clones not being tracked by Dyad, this means that there were 276 Leda clones in total.
The Number Of Castor Clones Is Uncertain
There were six Castor clones featured in Orphan Black: Mark, who was sent to infiltrate the Proletheans and ended up joining them; Styles, a soldier who tortured (and was killed by) Helena; Rudy and Seth, two clone brothers who were very close; Parsons, who was subjected to sickening medical experiments; and Ira, who worked directly with Susan Duncan, the scientist behind the Leda and Castor clones. There was also another Castor clone called Abel, who died as an infant. The Castors were afflicted with a fatal genetic disorder that caused seizures and extreme pain, as well as causing any women they had sex with to become sterile. Even if they did exist in similar numbers to the Leda clones, it's likely that most of the Castor brothers died from their disorder either before the events of Orphan Black, or not long afterwards.