Suetonius’ Lives of the Caesars usually begin with a family tree. These family trees are often rhetorical, foreshadowing in the ancestors character traits that will be themes of the rest of the Life. This particular rhetorical strategy relies upon an older phenomenon of ‘family identity’—namely, the literary application of similar characteristics to people in the same family—such as the one that tells us that the Claudii are proud and the Domitii Ahenobarbi are ferocious. Gary Farney studied ‘family identity’ as a phenomenon of the Republic. There, it was the association of a family with a certain characteristic, a kind of ‘branding’. It would be perfectly obvious for Suetonius to use the family identities already in use for well-known families, but, as I show here, Suetonius’ selection of ancestors creates different family identities rather than simply using the traditional ones he would have found in other sources. In this study I concentrate on Nero and Tiberius. I focus on these two emperors because they are individuals where there is a known family identity in other sources and they also have the most detailed and elaborate ancestry sections in Suetonius’ Caesars. Family identity seems to be most interesting to Suetonius when it goes against expectations, and that is when Suetonius’ family trees are most elaborate.