I only know what my Mom says... She says he's been unfaithful, but I refuse to accept that as fact without being able to hear what he has to say... He's been a jerk in the past, but over the last number of years, he's really calmed down and grown in the Lord... While it's not impossible for a Christian to commit adultery, at the same time it is possible for another Christian to let suspicion and misunderstanding get a hold of them, and to cite one sin (say, lying) as proof of another (an affair.) In any case, this is a really bad situation... Even if he did do it, I still don't think that has to mean the end of their marriage... They've been together for over 25 years... I'm sure they would need a lot of counseling, but I know I would want to forgive my wife if she was unfaithful... It's because people make mistakes, and I don't think mistakes have to necessarily be permanent.
That's what I have to say, and obviously Jesus did give permission for divorce on the grounds of infidelity, but I don't believe this was a command by any means, and he would still rather the couple stay together and the guilty person seek forgiveness and reconciliation.