Agree with the rest of the repondents

Refuse to take sides. Asking you to be involved is not the same as demandig that you be involved. Politely decline. Offer no explanation other than "I don't want to get further involved" (which is the truth it seems from what you have written here. I am sure that both sides are perfectly capable of carrying on without your direct support. The fact that it weighs heavy on your mind shows that you are indeed a man of honor. I think that if either side knows your story, you will be relieved of any pressure to take a side. You have so much in your RL to handle, that you definitely do not need to add other people's problems to your own.