two black dots in sky flying symmetrically and flashing blue at beginning of sighting.

me and my brother (Me - 12 Him - 7) saw two black dots flying completely symmetrically and at the exact same speed, when we first saw them they were flashing blue, but then stopped after around ten seconds, we could only see them when they were in front of a cloud but when they went in front of the blue sky they were impossible to see, they couldn't have been drones because it would take an extremely skilled person to fly a drone completely symmetrically and at the same speed along with another person doing the same thing, also they were too far up to be looking down with cameras (around 2,500ft up) they also looked like black dots, though I couldn't tell what shape it was.