Much of Janitor's life isn't really known for certain. A well-known liar, he is notorious for telling tall tales about himself; since nobody believes him, it is difficult to determine which stories are true. The dubious claims he has made over the years include:

He claims to have a twin brother, but later admits it to be an attempt at tricking J.D. and Turk.

He went to Harvard

He went to Yale

His wife only has a "pointer" on her right hand and "thumb/pinky" on her left

His grandfather was apparently abusive and would beat him with a gym sock full of nickels. This behavior was attributed to his grandfather's OCD, which may or may not be a correct diagnosis

He has told Elliot that he has a "sister-mom" and "brother-dad" in what might have been reference to Jack Nicholson.

He has told J.D. that he has a brother who is a stripper

He has a cousin, who is a bank teller, that supplies him with an exploding ink cartridge to find out who keeps disconnecting the security alarm

When he was a child, his mother kept him in a 'playpen' a.k.a. a 'baby cage' (a dog kennel). (This appears to be false until the end of the episode where he is arguing with his mother over it.)