I am divorced from my children's mother. We have joint custody but I am the primary custodial parent. The problem is their mom doesn't always come get the kids on her weekend. Then she'll appear on a weekend that is not hers and want them. Do I have to let the children go if it is my weekend and she didn't come on hers? Also, my 12-year-old son doesn't want to go to his mother's house. If he's determined not to, do I have to force him into the car?