What is the next number in this series?

There once was a man who was so proud of the fact that he had six kids that he insisted on calling his wife "mother of six."

His wife hated this name and asked him repeatedly not to call her that, but he was a stubborn man and was very proud that he had six kids.

One evening they were at a dinner party for his company and it was getting close to the time that they should be leaving. The husband yelled from across the room over to his wife, "mother of six, are you ready to go?"

Annoyed with his question, she responded, "In a minute, Father of four."