Need Advice....

So my dad died when I was young and I was raised in a single parent home.  I've never witnessed the dynamics between a married couple and I have never had to deal with the idea of seperation.
Now Joey is the youngest of three and he is 26.  The other day he and his dad were out golfing, and his dad casually tossed out that Joeys mum, Jane, was talking about moving out. 
So tonight, while shopping, Joey took much the same approach and casually tossed out that his mom is considering leaving his dad.  End of facts.  That was it, then quickly onto what sort of shampoo we should buy.
Me being me I backtracked.  Waitwaitwait....his parents may be splitting?  They have been married for 40ish years.  They have raised three kids together, they are raising two of their grandkids.  Joey has always had the whole family package.  And now he just casually mentions it may be over??
His mom has been really happy the last few times I've talked to her.  Don't know if it's because she has finally decided to leave, or if it's because she and Dave decided to work on things, seriously.
But my question is, how do I talk about this with Joey?  I know he needs to want to talk about it, so I shouldn't push him...but what do you say?  I could offer 1000 condolensces if he was to loose a parent (knock on wood) but I'm lost about how to deal with his parents seperating. 
It may seem like a silly thing to worry about.  But I've dealt with death, addiction, homelessness, abuse.  But divorce scares the shit out of me!  It's one of the reasons that I have yet to agree on a wedding date with Joey.