Cloud and Tifa want a baby. But Cloud is infertile. To get a baby, Cloud tells Tifa to have sex with as many men as possible until she gets pregnant.
http://www.fanfiction.net/s/3656499/1/Seed
I'm sorry, but WTF?
And because morbid curiosity got the better of me:
Cloud, to Tifa: "I promised I'd give you babies, and babies I will give you, even if it's only by my permission. Don't you see? It's the only way!"