I am in a fairly similar situation. I had to get and OFP against my childrens father so they currently arent seeing him at all until he too gets the treatment he needs to get better. They have a little sister whom they also dont get to see and as hard as it is we just have to remind them that this is Only temporary. I let my children write letters,or journal of some sort to at least let those feelings out. Also every time he gets sad or misses them..tell him to look at their pictures (if he has any) and send Love their way! Let him know each time he sends love their way itll help him and them miss each other less and less :) It gives their feelings some kind of validation at that point.Reminding them that they are not to blame,rather they need to be strong Root for them to get better so they can all be in each others lives again! :) I hope some of this helped..I know it can be hard being thrown into situations where we have no control,but as long as we continue to show love,comfort,protection and support..these kids will get through it a little easier!