US Census records before 1880 do not give relationship to the head of the household. The oldest male and female are often husband and wife–but occasionally they are siblings or there is another relationship.
If other records provide evidence that the oldest male and female in a household were married, remember that the children may not all be theirs together. Some could be his, some could be hers, some could be theirs, and some could have another relationship to one or both of the oldest male and female in the household.
Remember the pre-1880 US census indicated who was living in a household. That household may have been a married couple and their children (sometimes referred to as the “traditional household”) or another set of relationships. Those “non-traditional” households were not as unusual as some may think.