http://revach.net/article.php?id=4035

Section:  Avodah   Category: Chanoch L'Naar
Parshas Ki Seitzei: Both Parents With The Same Voice, Appearance and Height??

The braisa in Sanhedrin 71a says that there never was and never will be a Ben Sorer U'Moreh because in order for this wild child to be put to death his parents need to be similar in voice, appearance, and height which simply can't be. Why not? True it is rare but how can the Tanna say so with certainty.

The Baalei Mussar say that the Torah is teaching us a valuable parenting lesson. Often the parents each have their own agenda and their own set of priorities and fundamental beliefs. This sends the child conflicting signals and conflicting guidance and it leaves the child confused. Surely a child with such an upbringing is capable of misbehaving. His veering from the path is not a sign of internal rot. It is a ramification of poor chinuch for which the death penalty is not warranted.
But if the child has two parents that are on the page, they speak in similar tones, they both show the same appearance by acting in a similar manner to that which they demand of their child, and they both set the same goals and heights that they want their child to reach, and with this beautiful consistent easy to understand chinuch the child still leaves the right path, then there is something seriously wrong with the child in his soul and in his core. A child like that is better off dead.

To this Rebbi Shimon says emphatically, impossible. Every Jew has a pure neshama and if his parents present a united front and set a good example to follow the child will absolutely not behave in this way and therefore Ben Sorer U'Moreh can never exist.