For a man if he want a family he would need to date and have children with a woman between the ages of 21 to 34
The average age of marriage in America is 28 for a woman and thirty for a man
For me personally I find an older woman a lot more interesting and in some cases put together then a young woman
But their the issue of the impact of aging on fertility and sexual activity
And that as people get older they get set in their ways and it's very hard to change that goes for men and women
When I was at University my girlfriend was 27 years old and I was 18 if I was 21 years old think would have worked out better