What a dimwit. They have personal motivation to back up their brother. How can that not get through to you, even on the third explanation?
You assertion that I've "changed" anything proceeds from that basic confusion on your part. Their testimony is "suspect" because personal considerations would motivate them to support their brother. Another name for "personal considerations" is "self-interest"; actions motivated by self-interest are termed "self-serving"; when testimony is "self-serving" it is consequently "suspect".
I had hoped that inserting the word "suspect" would trigger a certain thought process on your part. Something like this: "Oh, yeah! I can think of parallels in which I would regard corroboration from a family member to be suspect! I wonder why that is? Um, I know! Because family members are motivated to back each other up! Perhaps, just perhaps mind you, but perhaps that's what Mr. Shalom meant by 'self-serving' testimony. I wonder...."
Sadly, the bulb didn't go off over your head. It's either broken, or of insufficient wattage for you to see the light.
Now, I can ask, 'And what was in it for Michael'?