affair

Sorry but I don't think its her job to think about HIS kids. he should have thought of the consequences of his actions before he decided to do what he did.

If the wife were to divorce the husband, would you blame her? For driving him to cheat, for taking her children away from the father?

In any case if the OP she does not have solid proof (and without solid proof u can't be 100% sure of anything) , she should really stay out of it, to protect herself.