This is just a wild guess, but I doubt Dennis is leaping to the defense of his brother.
There’s nothing much out there beyond tabloid gossip on that topic:
http://perezhilton.com/2009-09-28-dennis-quaid-estranged-from-brother-randy
Interesting that all three of those seem to be based on the same source material from a private eye.
Here’s another that appears to be based on comments directly from Randy. Randy is afraid Dennis will also be hit by the Star Whackers, but Dennis seems to have doubts. Go figure.
And I think Randy Quaid has claimed to be all of the above.
Gee, glad I didn’t take that role in The Debtors! Wouldn’t want to have been mixed up with all these nuts! 
Couldn’t get that to play, here’s a YouTube clip.
He seems amazingly sane in that clip. Almost maddeningly so.
I know this story is a couple of weeks old but maybe there is something to starwackers theory.
Link.
I only get wacked by stars in my fantasies, so I guess Randy and I have something in common.
If banging is the same as whacking, me too.
Eww… who wants to bang Randy Quaid?
More on the Quaids and their possible joint mental illness:
Dennis Quaid opens up, just a little, about his troubled brother: http://www.people.com/people/article/0,,20478363,00.html
Well that’s not saying a whole lot. I hope Dennis is trying to help, but maybe there isn’t much he can do, either.
I am so tired of these celebrity tattletales. Just last week Madonna let slip that the sky is blue!