The legitime of the parents who have an illegitimate child, when such child leaves neither legitimate descendants, nor a surviving spouse, nor illegitimate children, is one-half of the hereditary estate of such illegitimate child. If only legitimate or illegitimate children are left, the parents are not entitled to any legitime whatsoever. If only the widow or widower survives with parents of the illegitimate child, the legitime of the parents is one-fourth of the hereditary estate of the child, and that of the surviving spouse also one-fourth of the estate. (n)