Many people ask if an adulterous relationship will cause a parent to lose custody and the answer is it depends. In Georgia you have to show evidence of a true physical relationship as well as that this relationship was the cause of the divorce. If these elements are present merely having an affair does not make you an unfit parent and the court will not consider the action in itself when making a determination. However, what the court will consider is how the behavior has affected the children and whether the children have been exposed to this behavior. I have had cases in which one parent was so blatant in their behaviors, going so far as to bring the children to the hotel, that the judge easily granted full custody to the other parent.
Usually it is not so transparent and the case degenerates into one in which the betrayed spouse seeks revenge, the violating spouse claims innocence and the children are devastated by the process. What I can say to anyone seeking an answer to this question is that if you have children, divorce before you enter into the extramarital relationship.
No attorney can make a guarantee and no attorney has all of the answers, no matter what we think of ourselves, but if both parents are decent people and the only factor that the court has to consider is the affair of a parent and the cause of the dissolution of the marriage it is highly likely the court will weigh in favor of the injured spouse when determining custody. And, because courts do not tend to be creative in custody matters, it is highly likely the result will be every other weekend visitation for the spouse who was looking for love in all the wrong places.