I have neighbors (my parent's neighbors actually) who were married, had a son, divorce when he was very young. They were divorced for 9 years. He was engaged, never went through with it and the neighbors remarried, had three more sons.
A good friend of mine from college....his mom and dad were married for 2 years. Divorce. She remarries, has a son, divorces. She remarries her first husband and they have my friend. He loves to tell that story.
It does happen.