in Suetonius' history of "the lives of caesars" he suggests that Brutus was Caesars son. Suetonius says that Caesar had an affair with Brutus' mother and that after being stabbed he said to Brutus "you too my son" not "you too brutus."
Is this backed up by any other contemporary roman histories/accounts? is this account accepted by any reputable experts? what else has been written about this? thanks.
Goldsworthy explicitly names the supposed relationship a myth in his biography of Caesar. Meier doesn't bother to mention the supposed relationship at all. Mary Beard in this piece raises the issue only to suggest a better translation:
Classicists are forever pointing out that “Et tu Brute” were not actually what the ancients said that Caesar said as he died. The best bet is that he said to Brutus (in Greek) ‘kai su teknon?’ or ‘and you my child?’, fuelling the suspicion that Brutus was actually Caesar’s illegitimate son (‘teknon’ could be literally ‘son’ or a more general term of affection for a younger man).
Bourne, in a 1977 article, also read the expression as one of friendship rather than blood relation (this is the JStor link, if you have access).
If any scholar thinks Caesar was Brutus' father, I don't know them.
Brutus was almost certainly not Caesar's son.
In his Life of Brutus (5.1-2) Plutarch says:
"It is said, moreover, that Caesar also was concerned for his [Brutus'] safety, and ordered his officers not to kill Brutus in the battle, but to spare him, and take him prisoner if he gave himself up voluntarily, and if he persisted in fighting against capture, to let him alone and do him no violence; and that Caesar did this out of regard for Servilia, the mother of Brutus. For while he was still a young man, as it seems, Caesar had been intimate with Servilia, who was madly in love with him, and he had some grounds for believing that Brutus, who was born at about the time when her passion was in full blaze, was his own son."
Caesar's actual paternity, however, is quite unlikely. Plutarch, writing a century and a half after Caesar's death, was probably only reproducing rumors he found in his sources.
According to his entry in the Oxford Classical Dictionary, Brutus was born around 85 BCE (when Caesar was 15), and his father was generally assumed to be his namesake Marcus Iunius Brutus. We do not know when Caesar's protracted affair with Brutus' mother Servilia began, but it was almost certainly later.
Caesar's feelings for Servilia (which continued long after their affair ended) are an adequate explanation for the special favor he always showed Brutus.
Brutus and Caesar, in fact, remained on generally good terms almost to the very end - and it was this close acquaintance, not some long-concealed suspicion of paternity, that led Caesar to exclaim "You too, my child?" (if indeed he said it - Suetonius (Life of Caesar, 82.2) doesn't seem sure, and Cassius Dio (44.19.5) is equally ambivalent).