One night a boy brought a girl home for dinner because he really liked her and wanted her to meet his parents.
After dinner the boy's father says,
"Son, come here, I need to talk to you."
"Yes dad?"
"Son, you can't like that girl."
"Why not?"
"Don't tell your mom but she's your sister but your momma don't know."
"Oh, okay... :/"
Thus he stops liking her.
The next month the boy brings a second girl home for dinner because he liked her more than the last girl.
After dinner the boy's father says,
"Son, come here, I need to talk to you."
"Yes, dad?"
"Son, you can't like that girl."
"Why not?"
"Don't tell your mom, but she's your sister also but your momma don't know."
"Oh... okay... :/"
Again, devastated, he stops liking her.
The next month the boy brings home a third girl for dinner because he REALLY like her. He liked her so much that he wanted to marry her.
After dinner the boy's father says,
"Son, come here, I need to talk to you."
"Yes, dad?"
"Son, you can't marry that girl."
"Why not?"
"Don't tell your mom but she's your sister too, but your momma don't know."
"But dad I realllllly love her!"
"Sorry, kid."
He mopes around the house for a few days until his mom decides to ask him what's wrong.
"Baby, what's wrong?"
"Mmmm, I can't tell you mom."
"Why not?"
"Well, dad told me not to tell you."
"Come on you can tell me."
"Okay, well the first and second girl i brought home are my sisters!"
"oh, that man, I can't control him.."
"And the third girl, I REALLLY LOVE HER and she's my sister too..."
"I see...."
......
"You know what baby? You go ahead and marry the last girl because your daddy ain't your daddy but your daddy don't know."