I'd say the main thing is to let them each know you're not choosing sides and you value each them as a friend. It's a difficult road that lay ahead and I'm sorry I can't offer any more advice.

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Put me on wheels and I'll turn tricks.

Clever? Nah, I ran out of that years ago. But if you find this, let me know, k?
"The road goes ever on..." ~ Tolkien

In memory of my friend skip...
Go then, there are other worlds than these