The lists of the Twelve are slightly different from one gospel to the next. Traditionally, we've dealt with this by saying things like, "Thaddeus, also known as Judas (not the Iscariot one!)."
But I wonder if it was symptomatic of a fight, or a disagreement about who Jesus called the Twelve. Was there a thirteenth wheel in the group?
It's all soap operatic speculation to while away a Friday afternoon.