Our moon was most likely formed when Earth was in its molten sate. An asteroid hit Earth as it had done plenty of times in the past and knocked a huge rock into our orbit.
Whose to say there wasn't more than one rock ejected from Earth?
The reasons they aren't here today might include:
1) They were smaller and were knocked way off, to far to be pulled in to our gravitational pull
2) They might have over time conjoined with our moon or Earth
3) Possibly destroyed by an asteroid
TC


