To answer your question: The father would be able to file for custody of the children since you currently have no agreement or court order. If he can show that it is in the children’s best interest to have shared time with the parents he may get the current arrangement modified. Your ex would file, then after several months of arguing over all the dates and details, spending thousands of dollars on an attorney, you would go to mediation. If things are not decided in mediation, you would have a hearing set before a judge to see if the case needs to be decided in court. At this point, whatever agreement you make is signed off by the judge and becomes an order. My thoughts are normally to suggest filing for primary custody and settling for joint custody. But again, that is after a lot of time, stress and money from both sides are invested. A lot of courts are leaning more towards joint custody but they will not normally rule on that.
Is there a valid reason that you could give the court for not wanting to allow shared custody? Other than the current situation working…most situations can work if you give them a chance and the parents don’t let their feelings towards each other cloud their judgement. The best scenario is for both parents to be as involved in their children’s live as possible. Just because you lost your spouse does not mean that a child should lose that parent. Regardless of who’s “fault” the separation and divorce were, the children have the right to be with both parents. Joint physical & legal custody with equal time is what’s fair for the children. That’s just my opinion as I said and it takes a lot of cooperation with the other parent in order for the parents to make it work for them.
While there are no laws against cohabitation, there are judges who will still look at this situation with the bias of morality. The argument between living with someone and being married to them when children are involved is always going to be a sticky situation. You have some judges who realize that times have changed and that there are a lot of couples who never marry…but then you have some that stick to the belief that there’s an order to things and thier moral compass is going to point them to the party who is not doing this. The child’s best interest can sometimes include trying to decide if it’s best to allow them to be exposed to the real world. In other words, while it can be brought up in court that you living with your boyfriend that you had an affair with while you were married to the father, there is legally nothing that can be done about it. The judge is the one that ultimately decides and sometimes you have a judge that will be influenced by what you have subjected the children to previously…
I would suggest you getting an agreement and seriously considering joint custody for the children, if your ex even wants that. There are some who have primary custody but the parents actually share time, and there are some who have joint custodty with one parent having the children the majority of the time. Joint physical custody means what you make it mean in an agreement unless it states, “equal time”. An agreeement will sometimes keep things out of court down the road…even though custody can still be filed for later, it’s more difficult to change if there’s been an agreement.