Some physicists and cosmologists claim a multiverse, or parallel universe theory. Unfortunately for those that advocate these theories, there is no concrete, physical evidence of any kind. The most recent piece of "evidence" (I'm aware of) is from Ranga-Ram Chary from the California Institute of Technology. He thinks our universe is "bumping" into another one, as he was found a "bruise" in the cosmic background radiation of the universe. However, Joseph Silk of Johns Hopkins University in Baltimore, thinks this is a hasty conclusion, and that the "bruise" is due to foregrounds. Even Chary himself finds a 30 percent chance that what he's found is only background noise, and not evidence of a neighbouring universe at all.
Just as above. There is no evidence. All evidence points to a beginning. At Hawking's 70th birthday celebration, Dr. Alexander Vilenkin pretty much layed to rest the multiverse theory, concluding "All the evidence we have says that the universe had a beginning."
http://www.blogos.org/compellingtruth/multiverse.html