The D.C. Comics universe saw Batman and Robin face the villainous pair of the Joker and Harley Quinn, or Harley Quinn and Poison Ivy.
In J.K. Rowling's fictional Wizarding World about a certain boy wizarding growing up, Lord Voldemort was sometimes partnered with a Death Eater named Bellatrix Lestrange.
But what about our favorite pony universe (Equestria)?
A villainous, male/female pair-up of pony villains? Siblings of two of the Mane Six? Fluttershy's brother has publically been announced at San Diego Comic-Con.
But what about a sibling of Rainbow Dash? A sister, maybe?
Let's presume Flutterbro is the same age as his sister, they being fraternal twins.
As for Rainbow Dash's sister (let's call her Dash Sis), we'll assume Dash Sis is Rainbow Dash's older sister.
Flutterbro has the ability to summon and control swarms of flying creatures (birds, insects, and bats) to harass and confuse opponents.
Dash Sis has the ability to generate violent weather like hurricane winds, lightning, ice shards, and tornadoes.
Both Flutterbro and Dash Sis are a true pair of dangerous Pegasi.