What are the odds of someone being faithful during marriage, if they were unfaithful while dating the person they eventually married? He says that marriage is "different" and the ultimate commitment... and claims that he will be loyal during marriage? Can being married actually change someone and rid them of the desire to cheat?

That's an impossible question to answer. On one hand people can change. However, on the other hand it gets proved everyday that just because someone is married it doesn't stop them from cheating.

Also, I feel that the first time a person cheats is the hardest after that, it becomes easier. What is the likely hood of a person with the history of cheating, given a few rough patches in a relationship, to do it again? I have only been cheated on once and that was more than enough for me. Within a couple of days I was packed , out the door and never saw her again.

Who knows, I think that if you are committing yourself to someone who has cheated before you better have your RADAR on. Not that you should be paranoid. But, that you should definitely not ignore any flags. I admit, for me I would feel as if I was taking a risk.Then again how many people actually admit to cheating or have been caught for that matter. So , you just don't know.

Can being married actually change someone and rid them of the desire to cheat?

They may change, but I wouldn't bet my life on it, or marry them!

If a person doesn't have the moral character before marriage then they won't afterwards. That just my opinion. If they didn't respect their commitment before when they were in a serious relationship, what does having papers between them make a difference. It comes down to their ability to be a honest person, if they have proven you cannot trust them, then the question is WHY would you believe them about keeping vows. Once is ignorance, second is stupidity, third is plain asking for it.