Dear Annie: My oldest son is 43. He lives in another state. He has a girlfriend that he lives with. They are serious but not married, but they do plan to get married. The girlfriend has four children, ages 22, 21, 14 and 12. My son wants to come visit. He has two kids. One is 18 years old (adopted through a previous marriage), and one is 7 years old (biological daughter from another marriage). …