瑜伽師地論略纂 16.3

16.3

論云「不相似子」者，謂是下賤人，生與王不相似故也。相似子者，是王真子，與王相似，以形儀等，與父相似，人皆愛之，無詈容言也。

The treatise states 'dissimilar son': this refers to a person of low base birth who, upon being born, does not resemble the king. A 'similar son' is a true son of the king, who resembles the king; because in bodily demeanour and so forth he resembles his father, everyone loves him, and there are no abusive looks or words toward him.