I am pretty sure that females most fertile times are between the ages of 20 and 26. That's at least according to one study I read.
Back in the "Good ole days", my ex's great grand parents, who had somewhere around 4 or 5 children and stayed together until death had an age difference that wouldn't fly in today's times. He was in his 20's when they married, and she was 12. She had her first child at 14. It's really hard to fathom that now, because he would be doing 20 years in modern times, just crazy to think about. I guess he was established and had the means to take care of her...idk.