When you fuck your sister and she becomes pregnant. You both fuck the baby and turn it into a sex slave as it grows older.
My sister was sucking on my 16-inch long and 5-inch wide cock licking the cum off when she asked for a baby.
"Ahh~ if you want a baby then- mmh~ then take off you H size bra and sick harder you cum dumpster~"
"Yes daddy~"