Iokaste is a parent of Oedipus.
Iokaste is a parent of Polyneikes.
Oedipus is a parent of Polyneikes.
Polyneikes is a parent of Thersandros.
Oedipus is a patricide.
Thersandros is not a patricide.
Everybody who is a parent of a patricide who is a parent of somebody who is not a patricide is an answer.