In the scene where the moon with the comet are shown together, comet's tail points away from the sun. The bright side of the moon also faces the sun. Normally, the bright side of the moon and the tail of the comet would both indicate the approximate direction of the sun. The relative to each other, bright side of the moon and the orientation of the comet's tail depict an impossible location of the sun. Either the moon or the comet was placed into night sky with the incorrect orientation.
Elena twice says that Stephan never mentioned that he had a brother (once to Damon, then later to Stephan). However, in the previous episode when Caroline, Bonnie and Elena are asking Stephan about himself, Elena asks if he has siblings. He replies that he has none that he talks to, implying he does have siblings. Therefore, Elena shouldn't have been so surprised that Stephan does have a brother.