Can satellites travel in clusters? Last night we saw a large cluster of what looked like exceptionally bright stars that moved, as a group, across the night sky in Lancaster, PA. It was about 9:15 pm, and they moved roughly from SW to NE. There were 25 or 30 of them. They moved as quickly as a satellite I once saw, but were bigger and brighter. They were soundless and did not blink, and the relationships between the lights changed slightly as they moved.

We don't believe in UFOs, but can't we find any explanation via google. 

Can that many satellites move as a group?
Yes, they can.  The ships that visit the ISS often orbit near the station for several hours before docking.  Further, there are several satellites that travel in pairs or trios with other satellites.  The nearer the satellites are to earth, or the farther apart they are, the more difficult the task of maintaining spatial relationships between the spacecraft. This is because the spacecraft must be in the same orbital plane to travel together.  The most common configuration is where they are in the exact same orbit, with one satellites a few seconds ahead of the other along the same path.