Salve Piscine,
It's been a while since I had any Greek, but from my understanding "teknon" is the past participle of "titenai" (hellenists please correct me if I'm wrong!) which means "to bear; to bring forth; to produce (in an organic sense)". So "teknon" means "that which has been produced, which is born."
So, "me teknon" should be "my 'product'" (ugly translation but hey
). Has Caesar used the word for son, "huios", one could have supposed that he meant son in a spiritual sense or perhaps an adoptive sense, but I don't think there's any doubt about the word "teknon".
I have no idea where "et tu, Brute" comes from. Perhaps a different source reporting on Caesar's death?
Vale bene,
Draco
Gn. Dionysius Draco Invictus