I've been in your situation before ... If you meddle too much, everything ends up being your fault, so be careful OP ! And good luck ! It's a horrible situation to be in, I hope it gets better soon :)

Tell me to put their grownup pants on and quit complaining to you. Tell them all about their making you the third wheel, should help a bit

That's never a good position to be in. And don't start repeating what the other person says either.

Just ne a listening ear to each one, hopefully they'll get back together soon..

I think I see the problem here... They both seem to be under the impression to you want to listen them talk about the other. You should probably correct that... or sit there in silence until you finally explode at one of them.

That's why I don't have friends....

Now you know how Harry Potter felt in year 3 and 6 ;) Anyway, you need to tell them that you're not going to pick side and that if they want to keep you as friend, they need to refrain bitching about each other to you.

Tell both of them that they are both your friends, and that you are not going to choose a side, because they both mean a lot to you, so to please quit telling you bad things about the other. Breaking up hurts, and you're there for both, but don't want to hear negative things about either, since they are your friend.

I know exactly how you feel. It sucks being the middle man. It's best to just not take sides and remain neutral about the subject to both of them. It's what I did.

This was Harry Potter's worst fear too.