Read the following article and answer the question.

Had he been of a mind to , Zexion would have approved the taste of whoever had chosen the decorations , but he was in no mind to approve of anything and therefore did not . Lady Nocturne descended the stairs gracefully , leading her son by the hand . Zexion recognized him at once , of course . He could not imagine forgetting that face , once seen . Not that it was a particularly noticeable face : blondish hair , eyes of some light shade , a childishly tilted nose and too wide a smile .

What may be the reason for recognizing the little boy he never met ?
That 's his son .