If the new partner makes the children feel uncomfortable, whether it has to do with the partner personally or it's related to the children feeling that the partner may be at fault or contributing to the separation and divorce, this is likely to have an effect on custody decisions made by the judge.
As such, a spouse who decides to date during the separation is wise to keep the children and the new partner separate to avoid arousing these types of issues during the proceedings.
The cheating spouse and the third party do not necessarily even have to have a sexual relationship – in some places, a family member who convinces one spouse to leave the other might be liable for alienation of affection (though this is very uncommon).
Another, even less common, suit is one for "criminal conversation." In a criminal conversation suit, the wronged spouse again sues, but for the suit to proceed there must have been a sexual relationship.
During the proceedings, the fact that a dating spouse is already separated will be noted, but that does not necessarily mean the circumstances of the new relationship will not be considered.The other spouse, if they are not dating, may develop the idea that the dating spouse was committing adultery even if that idea hadn't surfaced before.Or, the other spouse may simply suffer anger and hurt as a result of the limited amount of time it apparently took the dating spouse to recover and move on.Either way, the other spouse may become confrontational, may become unwilling to compromise and obstinate during the proceedings, or, at best, may become cold and distrustful of the dating spouse.These feelings can cause property division to be more difficult, as well as other aspects of the divorce.For example, the judge might disapprove of the dating spouse's behavior and develop a bias against them.