Did Thomas have a Twin (his name Dydimus = Twin)?

It is not known whether or not Thomas had a twin. However, he could have. In biblical times and hundreds of years since, names were given to people to describe a quality or trait that individual may have displayed. In-fact we do it today; Thomas was much like a nickname. His real name was Judas, Thomas may have been a surname given to him to describe the fact he had a twin. Some legends say he had a twin sister, Lydia.
Good question. I had to do a lot of looking for this one. One thing to remember from something like this is that it is easy to get caught up in side questions. If the Bible mentioned it, we should learn it. If the Bible didn't mention it, we should not concern ourselves with it.