Father : "That's great son. Who is she?"
Son: "It's Tina, the neighbor's daughter".
Father : "Ohhh I wish you hadn't said that.I have to tell u something son, but you must promise not to tell your mother.Tina is actually your sister."
The boy is naturally bummed out, but a couple of months later
Son : "Daddy, I fell in love again and she is even hotter!"
Father : "That's great son. Who is she?"
Son: "It's Peny, the other neighbor's daughter."
Father : "Ohhhh I wish you hadn't said that. Peny is also your sister."
This went on couple of times and the son was so mad,he went straight to his mother crying.
Son : "Mum I am so mad at dad ! I fell in love with six girls but I can't date any of them because daddy is their father!"
The mother hugs him affectionately and says:
"My love, you can date whoever you want. Don't listen to him. He is not your Father."!!!