For a generation of researcher, it was assumed there was a hard and fast process of courtship, marriage, and then reproduction. It was the Victorian way...
Ancestors may have not been weighted down by this process in the way later generations were. Especially in certain times: the 1770's-1880's were rich in this fact. "Ministers" and "Justice's of the Peace" were often slim on the ground. Local leaders were known to unite a couple because they knew their valley would be cut off for a long, long winter or some religious groups provided their own 'lay ministers' who served the needs of their people. Some did not seek secular recognitions for marriages at all. Then, when the trails or rivers were passable again, the visiting minister might have many couples to formally marry, some even with toddlers! Some early records out of Virginia, Kentucky, Tennessee, Missouri, and Arkansas reveal this type of event, as do records and journals of traveling ministers from Methodist and Baptist traditions.
As a result, a family might have a child born in 1808 but the marriage record located indicates a date of 1812! There must have been a previous marriage and they all died. Really? Maybe they were just experiencing the reality of life in remote mountain areas or areas with no regular person legally recognized to marry people.
Yes, sometimes nature takes its course and people will be people. Sometimes, it is our understanding of the proper process that is at fault. Be open minded and think outside the box we label as what is proper to discover the truth in the family story.