Parashas Acharei Mos · Passuk 18:21
Chabad.org — English translation + Rashi
Torah Temima points to Sanhedrin 64b.
English: One who passes all of his offspring is exempt — “of your seed,” not “all your seed.”
Partial seed required
Liability requires that some of the offender’s children remain; passing the entire progeny falls outside this formulation.