My wife is pregnant with another man's child

I know this sounds harsh but if I were in your shoes, especially if you have no kids with her, get a divorce. If you are going to stay in the marriage and let this man be involved, what does that make you of? Since she is carrying another man's son, you can use a lawyer against her and wouldn't have to pay for any alimony. If I were you, the child will never carry my name in case your wife tries to claim child support. It is going to be tough, trust me, I am speaking from experience. If the father isn't involved, perhaps I could reconsider if it a one-off affair. But you can't be certain that feelings will develop between the two because of the child.