If you have not filed for divorce, I recommend that you do that prior to moving in with your boyfriend. I did have a case where a male client had his girlfriend move in the house with him and the children before a divorce had been filed, and shortly after the wife had moved out. The judge did not like the situation and awarded temporary custody to the wife. How a judge will react depends on the judge, some have very conservative attitudes. At least if a divorce has been filed, it shows a clear date when the marriage was over. If you absolutely must move in with your boyfriend due to financial reasons, or to prevent the children from living on the street, then move in, but if you can afford to maintain separate residences until the divorce is over, I would recommend that course of action. You never know how your judge will react to the situation.