In pre-1880 United States census records, the relationship of household members to the head of household is not given. The individuals living in a household may be husband, wife, and their children. Or it may be husband, wife, some of his children, some of her children, and some of theirs. Or it one of the youngsters in the household may be a nephew or niece.
Or it may be something else. Just do not always make the assumption that every pre-1880 household is a husband, wife, and their children. It may not be.