The old saying, "Once a cheater, always a cheater" may not apply to everyone one but if you are in a relationship with someone who has cheated in the past it could be a warning sign of things to come if you should marry.
As Vicki Larson asks in a recent Huffington Post article, "Once a cheater, always a cheater? Who knows? The bigger question is, do you risk it?"
And that is the question you have to ask yourself when thinking about marrying someone with a history of cheating. Do you risk it? Will you be marrying someone who will cheat on you given his/her past relationship behavior? Bottom line, the only sure fire way to protect a future marriage from infidelity is to not marry someone with a history of infidelity.