Granddaughter loses virginity to her Grandpa. She loves it. She tries to figure out if it's real by having sex with a couple other guys. She found them okay. And she had to wait a month or two to get back with her Grandpa. He went on a long trip. She ends up having sex with him again. A few more times before she finds out she's pregnant with his child. Some time later she gives birth to his twins. Later on she continues having sex with him and gets pregnant with twins again. She becomes addicted to having sex with him and having his babies. Each time she has twins. Except one time.
Her family finds out that her Grandpa is the father of the babies. They force her to agree that if she has twins again with him she'll either have to have her tubes tied or quit having sex with him. Luckily she doesn't have twins. She has triplets. She finally moves in with her Grandpa and they live as husband and wife. She has his babies for years to come.