Conundrums

I have a very beloved uncle.  For the most part, he is made of awesome.  Unfortunately, stupidity makes up the rest of him.  I'd say he's 75% awesome, 25% stupidity.  And I've been very fortunate to only have to witness the stupidity from afar.  I've never been on the receiving end of his antics; quite the opposite, in fact, he's always been very supportive of me. 

About a year and a half ago, he gave his stupidity full reign (seriously, FULL reign) and literally destroyed his life over nothing.  He left his family, lost his job and every hope of ever entering his career field again, and landed himself in prison for 18 months.  

His wife, who is either the biggest saint ever or the dumbest chick ever (it's a toss up really.  I fucking adore her, but sticking with my uncle after his history is masochism on a level I have never seen....and I can't even begin to figure out what effect all of it will have on their children.) is sticking with him.  They have children who are around the same age as my children, and they are really struggling with everything.  My grandmother......is not helping (to put it very mildly).  

I said all that to ask this:  What the fuck am I supposed to write in a letter to him??  Seriously.  What do you write to someone in jail??  I know that he knows he fucked up on a nuclear level and is devastated by how everything is now.  I don't want to bum him out.  He's definitely paying for his actions.  My family wants me to write him....and I WANT to write him.  But I keep starting letters, realizing that they sound utterly ridiculous, and throwing them away.   I'm completely at a loss.