There’s a reasonable chance that your ancestor’s family of origin was a “his, hers, and ours” family. Death of a spouse during their childbearing years was not all that unusual before 1900 and for economic or social reasons, a widow/er with children frequently chose to marry again.
That may have resulted in a family where some children were the husband’s by a first marriage, some children were the wife’s by a previous marriage, and some resulted from their marriage to each other. Sometimes records will make this clear.
Other times it will not.
Keep yourself open to this possibility.
And it’s also possible that there was a child that resulted from a relationship outside of a marriage.