Who is a "mamzer"? All kin who are subsumed in "may not come." These are the words of R. Akiva. For it is written (Ibid. 1) "A man shall not take the wife of his father and he shall not uncover the lap of his father … (3) "A mamzer may not come, etc." Just as "the wife of his father" is distinct in being kin and subsumed in "may not come," and the child is a mamzer, so, in all who are thus characterized, the child is a mamzer.
Shimon Hatemani says: All who are liable to kareth (cutting-off) at the hands of heaven — the child is a mamzer, it being written "A man shall not take the wife of his father … A mamzer may not come, etc." Just as "the wife of his father" is distinct in being liable to kareth at the hands of heaven and the child is a mamzer, so, in all who are thus characterized, the child is a mamzer.