I think having kids before you are 30 is fine, but we had our second kid when my wife was 36 and it was also fine. I think when you get in your forties as a man or late thirties as a woman it can be tougher.

Also, adopt. Before I was a parent I thought of a child as "mine" because of biology. Really you see that you shape people and form a connection with them because they are part of your family.