Sometimes you can explain things to the child in a way that they understand. Sometimes mommy gets extra tired because the baby wakes her up at night so she needs to take a nap in the daytime therefore he gets to come to your house and play because he isn't a baby anymore that needs two naps a day so baby and mommy are at home taking naps and daddy is at work and he is being a big boy with no morning nap playing with his friends.