http://www.youtube.com/watch?v=eo0zFQkYsf4

http://blogs.nasa.gov/cm/blog/Watch%20the%20Skies/posts/post_1361037562855.html

Not only the space of the solar system, but the space of all possible orbital energies and orientations, is so vast that the probability of two rocks with a common origin going onto completley different orbits and then coming together again is too tiny for me to even figure out how to properly calculate. The profusion of rocks (many many millions the size of the small one, probably a million plus for the big one) from a huge number of sources means the odds of any two objects not on a very similar orbit having a related origin is basically nill.

Coincidence, as unlikely as it is, is orders of magnitude more likely than any other option.