Sanhedrin 28 - Relatives Disqualified as Judges or Witnesses
The disqualification of relatives is absolute: they may not testify whether their testimony is favorable or detrimental. The relatives include: one's brother, uncle, sister's husband, aunt's husband, father-in-law, brother-in-law, and also their sons and sons-in-law.
Rabbi Yehudah says: "One's close friend and one's enemy are also disqualified." But the Sages say that the Jewish people are not suspected of bearing false witness about someone because of love or animosity.
How does one understand " Fathers shall not be put to death because of their sons nor shall sons be put to death because of their fathers ..."? We already know that "... each man shall be put to death only because of his own sin ." Therefore, we have to understand that "Fathers shall not be put to death because of the testimony of their sons."
Art: Isaac Oliver - The Browne Brothers