My parents tried for YEARS to conceive until they were told it wasn't possible. They were very close to closing in on an adoption, and lo and behold, my sister came along! The parents couldn't financially support two babies at once (esp. since the one they were going to adopt was challenged) so they decided not to adopt. The girl actually ended up at school with my sister and myself. It's funny to think that she would have been my older sister had my biological sister not decided to make an appearance in this world
Then my parents got lucky and conceived me, and after the terrible baby that I was, they decided they'd had enough