I'm just going off of what I was told by my pastor, 25. He's had 27 years of experience working with the annulment board, and told me just last week that even "outside the church" marriages must be annulled. Now perhaps that is a recent ruling that wasn't in effect at the time your brother married in the church.
It's a subjective process totally dependent on how certain events or patterns in the relationship are viewed. So I could easily see the same case presented to different boards and getting different verdicts, much like in the regular legal system.
WAW Using God Me-43 W-40 M-14 S-11 S-9 D-7 EABomb 5/09 Separated 12/09