Considering they only have one line, John 14:22, between the both of them in the entirety of the Bible, I have no clue who they are or what they are about.
If you don’t know anything about the Bible, like me, you wouldn’t even know that the line they have was spoken by Thaddeus. This is because he also went by the name of Judas, which was the name used leading up to their line in the Bible. And how do we know that James was there when he wasn’t even mentioned in the surrounding scriptures? Why are the two associated together?
As disciples I imagine they were important to Jesus but only having one line kind of throws me off a bit. No one else except John mentioned them by name. They might not have been leaders or popular, but Jesus picked them for a reason right?