Your ancestral couple are enumerated in the 1850 US census with 13 children. Be careful drawing immediate conclusions–particularly because 1850 US census enumerations do not list the relationship of the individuals listed as living in the same household. Here are a few thoughts.
Do not jump the conclusion that the children all have to be the biological children of the apparent husband and wife.
Children living with a step-father during this time period may be enumerated with the step-father’s last name even if it that child never used that last name in other records.
The oldest man and woman enumerated are likely husband and wife. One or both of them may have had other spouses before 1850. An age gap may suggest the probable wife was his second, but age gaps between spouses should not cause you to conclude there was an earlier marriage.
Age gaps in the children may suggest a second marriage. They can also be because children died as well. A few older children could be younger siblings of the husband–it is possible that the “husband” was the oldest child in his family and that his parents are deceased or unable to care for their children who are much younger than their oldest child?
Are the ages of several children too close together? While children can be close together, six children in a five-year time span may suggest multiple marriages–or a set of twins (depending on the ages listed).
The key is to use such an enumeration to search for other records to flesh out details not given in the census–not to jump to an immediate conclusion and refuse to contemplate other reasonable scenarios.