Wiktionary
n. 1 A male biological child, whether legitimate or illegitimate, as opposed to one adopted. 2 An illegitimate son.
Wikipedia
Usage examples of "natural son".
William, king of Naples, died about the same time, and the pope intended to occupy that kingdom on the ground that the king had left only a natural son named Tancred.
And Paul had sensed the jihad in their words, shrugged off the question with one of his own--learning then that Kaleff, the elder of the two, was ten, and the natural son of Geoff.
And Paul had sensed the jihad in their words, shrugged off the question with one of his own -- learning then that Kaleff, the elder of the two, was ten, and the natural son of Geoff.
My preconceived notions of Dutiful, my possessive idealizations of what my natural son would be like, stood between me and the frail threads of the Skill-link I sought to untangle.