Depends on what you mean by 'forgive'. See for me forgiveness is something we do for ourselves, letting go of anger, pain, bitterness precipitated by the other person's behavior. It doesn't mean 'forgetting' or allowing the person to remain in your life in a way that they could hurt you. But then i've never been a jealous person. That annoyed the hell out of my very jealous first husband.
Which is not to say i'd have tolerated someone 'cheating' on what was supposedly a committed relationship. The lying, the lack of concern for not only my feelings but for my physical health (there were health risks pre HIV/AIDS but once that surfaced the risks greater. That would have ended it. But then i ended my 3rd marriage over incessant lies piling up along with one other factor i think i've talked about on long ago on another thread, that's irrelevant to this one.
But another question i have is, would you expect to be forgiven, by whatever your definition of that word is, if you cheated? This is an area of human relationships where double standards quite common.
My Dad was a good father, but not a faithful husband. For psychological reasons he frequently had a 'another woman' . Not excusing it, tho what i know of his upbringing explains it somewhat. What bothered me more and i later learned was common behavior in men who cheat was that he frequently accused his current wife of cheating. (He had 5 over the decades, i actually knew 2 of them besides my Mom who was his second.)
But i wouldn't allow someone else's unacceptable behavior to continue to cause me problems in the form of anger and bitterness whether we able to maintain our relationship or not. For that matter if one can't forgive (whatever the transgression) the relationship is likely doomed any way because the trust has been broken and it will be hard to re-establish since odds are the behavior will continue. People CAN change, but it takes powerful internal motivation to do so.