Jodie Foster, Sean Aston, Helen Hunt, Kirk Cameron, DiCaprio, Melissa Gilbert, Natalie Portman, Diane Lane......I could name a few dozen more if my memory was clear.
Clearly, not everyone is qualified to be a parent but there isn't a switch to turn of the egg or sperm production in humans.
There are also thousands of couples who would make fine parents who are unable to conceive. Sad really on both counts.