This can be created and recreated easily by taking video through a double glazed window, I've seen it so many times. Or sometimes the real sun is dim behind the clouds and a much brighter spot appears below it because clouds are made of just certain shape of ice crystals and they refract light making a bright spot that looks like the sun. But this kind of double sun only happens when there are clouds. To know the truth we need to konow where the video was taken and with what make of a mobile phone.