These Twin Astronauts Have The Most Epic Sibling Rivalry Ever

They may be astronauts, but they are also siblings.

Here are Mark and Scott Kelly. Scott is an astronaut currently spending a year in space. Mark is a former astronaut here on Earth. They are twins.

Mark is on the left, Scott is on the right. The fact that they are twins is super helpful to NASA, who will use Mark as a control while his identical twin brother experiences space for a year, giving scientists insight into what being in zero-gravity for long periods of time does to a human.

Robert Markowitz / NASA

In rare instances, their Twitter accounts are proof that neither is above some gentle smack talk between brothers, even when one of them is in space:

Marco Grob / NASA / Via nasa.gov

There was that time that Scott was reminded of brotherly "punch-ups" from their youth by a promotional poster:

Via Twitter: @StationCDRKelly

And there was a time when Mark expressed sympathy for the astronauts joining Scott on the International Space Station:

Via Twitter: @ShuttleCDRKelly

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