The Anniversary Dinner

Their three kids, all successful, agreed to a Sunday dinner in their honor. “Happy Anniversary Mom and Dad,” gushed their first son upon his arrival, “Sorry for running late. I had an emergency at the hospital with a patient, you know how it is, and I didn’t have time to get you a gift.”
“Not to worry,” said the father, “The important thing is we’re all together today.”
The second son arrived, “You and Mom look great, Dad. I just flew in from LA between depositions and didn’t have time to shop for your present.”
“It’s nothing,” said the father, “We’re glad you were able to come.”
Just then the daughter arrived, “Hello and happy anniversary! Sorry, but my boss is sending me out of town, and I was really busy packing so I didn’t have time to get you anything.”
After they had finished dessert, the father said, “There’s something your mother and I have wanted to tell you for a long time. You see, we were really poor, but we managed to send each of you to college. Through the years your mother and I knew we loved each other very much, but we just never found the time to actually get married.”
The three children gasped and said, “WHAT? You mean we’re bastards?”
“Yep”, said the father, “And cheap ones too.”