Social security number question?

I have a friend who gave one of his relatives his social security number. His relative is illegally in the United States. Recently my friend tried applying for a job and they turned him down because the business said he had worked their previously and had bad work ethics. My friend has never worked there before but his social security number said he did. I'm guessing that his relative used his number and now my friend has a bad reputation. My friend also claimed his relatives jobs on his taxes. Is there anyway to get back his social security number? Or possibly get a new one?